UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM N-CSR CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES 		Investment Company Act file number 811-01466 Pioneer Fund (Exact name of registrant as specified in charter) 60 State Street, Boston, MA 02109 (Address of principal executive offices) (ZIP code) Terrence J. Cullen, Amundi Pioneer Asset Management, Inc., 60 State Street, Boston, MA 02109 (Name and address of agent for service) Registrant's telephone number, including area code: (617) 742-7825 Date of fiscal year end: December 31 Date of reporting period: January 1, 2018 through December 31, 2018 Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles. A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget ("OMB") control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507. ITEM 1. REPORTS TO STOCKHOLDERS. Pioneer Fund -------------------------------------------------------------------------------- Annual Report | December 31, 2018 -------------------------------------------------------------------------------- Ticker Symbols: Class A PIODX Class C PCODX Class R PIORX Class Y PYODX Beginning in February 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund's shareholder reports like this one will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial intermediary, such as a broker-dealer, bank or insurance company. Instead, the reports will be made available on the Fund's website, and you will be notified by mail each time a report is posted and provided with a website link to access the report. If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications electronically by contacting your financial intermediary or, if you invest directly with the Fund, by calling 1-800-225-6292. You may elect to receive all future reports in paper free of charge. If you invest directly with the Fund, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 1-800-225-6292. If you invest through a financial intermediary, you can contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held in your account if you invest through your financial intermediary or all funds held with the Pioneer funds complex if you invest directly. [LOGO] Amundi Pioneer ============== ASSET MANAGEMENT visit us: www.amundipioneer.com Table of Contents President's Letter 2 Portfolio Management Discussion 4 Portfolio Summary 10 Prices and Distributions 11 Performance Update 12 Comparing Ongoing Fund Expenses 16 Schedule of Investments 18 Financial Statements 23 Notes to Financial Statements 31 Report of Independent Registered Public Accounting Firm 40 Additional Information 42 Approval of Investment Management Agreement 44 Trustees, Officers and Service Providers 49 Pioneer Fund | Annual Report | 12/31/18 1 President's Letter Since 1928, active portfolio management based on in-depth, fundamental research, has been the foundation of Amundi Pioneer's investment approach. We believe an active management investment strategy is a prudent approach to investing, especially during periods of market volatility, which can result from any number of risk factors, including slow U.S. economic growth, rising interest rates, and geopolitical factors. Of course, in today's global economy, risk factors extend well beyond U.S. borders, and political and economic issues on the international front can also cause or contribute to volatility in U.S. markets. At Amundi Pioneer, each security under consideration is researched by our team of experienced investment professionals, who visit companies and meet with their management teams. At the end of this research process, if we have conviction in a company's business model and management team, and regard the security as a potentially solid investment opportunity, an Amundi Pioneer portfolio manager makes an active decision to invest in that security. The portfolio resulting from these decisions represents an expression of his or her convictions, and strives to balance overall risk and return opportunity. As an example, the Standard & Poor's 500 Index -- the predominant benchmark for many U.S. Large-Cap Core Equity funds -- has 500 stocks. An Amundi Pioneer portfolio manager chooses to invest in only those companies that he or she believes can offer the most attractive opportunities to pursue the fund's investment objective, thus potentially benefiting the fund's shareowners. This process results in a portfolio that does not own all 500 stocks, but a much narrower universe. The same active decision to invest in a company is also applied when we decide to sell a security, either due to changing fundamentals, valuation concerns, or market risks. We apply this active decision-making across all of our equity, fixed-income, and global portfolios. Today, as investors, we have many options. It is our view that active management can serve shareholders well not only when markets are thriving, but also during periods of market volatility and uncertainty, thus making it a compelling investment choice. As you consider the many choices today, we encourage you to work with your financial advisor to develop an overall investment plan that addresses both your short- and long-term goals, and to implement such a plan in a disciplined manner. 2 Pioneer Fund | Annual Report | 12/31/18 We greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future. Sincerely, /s/ Lisa M. Jones Lisa M. Jones Head of the Americas, President and CEO of U.S. Amundi Pioneer Asset Management USA, Inc. December 31, 2018 Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund's historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results. Pioneer Fund | Annual Report | 12/31/18 3 Portfolio Management Discussion | 12/31/18 In the following discussion, Jeff Kripke and John A. Carey discuss the market environment during the 12-month period ended December 31, 2018, and Pioneer Fund's performance during the period. Mr. Kripke, a senior vice president and a portfolio manager at Amundi Pioneer Asset Management, Inc. ("Amundi Pioneer"), is responsible for the day-to-day management of the Fund, along with Mr. Carey, Managing Director, Director of Equity Income, U.S., and a portfolio manager at Amundi Pioneer, and Walter Hunnewell, Jr., a vice president and a portfolio manager at Amundi Pioneer. Q How did the Fund perform over the 12-month period ended December 31, 2018? A Pioneer Fund's Class A shares returned -1.74% at net asset value during the 12-month period ended December 31, 2018, while the Fund's benchmark, the Standard & Poor's 500 Index (the S&P 500), returned -4.38%. During the same period, the average return of the 1,402 mutual funds in Morningstar's Large Blend Funds category was -6.27%. Q How would you describe the market environment for equities during the 12-month period ended December 31, 2018? A The Fund's fiscal year ended December 31, 2018, featured a very volatile 12-month period for domestic equities. Domestic stock indices rocketed higher in January (up by more than 10%), sharply corrected in February 2018 and declined slightly in March, with the Fund's benchmark, the S&P 500, falling by more than 9% from peak-to-trough over the course of those first three months. The February 2018 market correction was driven by a sharp rise in the 10-year government (U.S. Treasury) bond yield, which started the 12-month period at 2.41%, but rose to 2.95% by mid-February. The increase in the 10-year Treasury yield was believed to be a result of heightened inflation expectations driven by wage-rate increases, which began to accelerate during the January/February period. Additionally, the Federal Reserve (the Fed) was, at the same time, signaling its intention to raise short-term interest rates throughout 2018 and possibly into 2019. After March, equity investors began bidding up stock prices again, due to strong corporate earnings releases over the first two calendar quarters of 2018. Equity returns during the April-September period were also buoyed by improved levels in both business and consumer confidence, which were the result, to a certain degree, of reduced U.S. business and personal income tax rates that went into effect in January 2018. Employment trends also improved over the first half of the period, with the unemployment rate reaching 3.8% at the end of May, a multi-decade low. 4 Pioneer Fund | Annual Report | 12/31/18 Market volatility returned after domestic equities peaked again at the end of September, however, as October saw another sharp market correction, with investors taking on a more defensive stance. The October slump was driven by concerns over the continued prospect for multiple short-term interest-rate increases by the Fed in 2018 and 2019, even as economic data (particularly in housing) was beginning to soften; the potential dampening effect on the economy and corporate earnings of U.S. tariffs and the threat of a possible trade war with China; and geopolitical issues such as the ongoing Brexit saga in the United Kingdom, among other headline-grabbing events in Europe. Volatility remained high over the final two months of the year, and after a better month of November, December saw the S&P 500 plummet by more than 9% as market participants seemed to obsess over the concerns mentioned earlier. The late-year slump caused the S&P 500 to finish 2018 down by more than 4%. Within the S&P 500, energy, materials, financial, and industrials were the worst-performing sectors over the 12-month period. Energy (-18%) was the worst performer, as oil prices declined, while the materials sector was down by nearly 15% and financials and industrials were each down by more than 13%. The S&P 500's best-performing sector during the period was health care, which was up by more than 6%, followed by utilities, information technology, and consumer discretionary. Q Which of your investment decisions contributed positively to the Fund's benchmark-relative performance during the 12-month period ended December 31, 2018? A The Fund was able to outperform the S&P 500 during the period due to strong stock selection results, particularly in the health care and financials sectors. Asset allocation was essentially neutral for benchmark-relative returns, but the Fund did benefit from an underweight to consumer staples, a sector that was down by nearly 9% for the 12-month period. We had underweighted consumer staples due to high valuations versus the organic growth prospects for companies in the sector, which we did not view favorably. Individual positions in the portfolio that aided the Fund's benchmark-relative performance during the period included Merck, McDonald's, CME Group (financials), and Microsoft. Shares of Merck, a global pharmaceutical company, outperformed mainly due to the continued strong sales of its well-known cancer drug, Keytruda. During the period, the Food and Drug Administration granted accelerated approval for Keytruda's use for patients with hepatocellular carcinoma. Meanwhile, Keytruda's competitors in the lung-cancer treatment area have lost a lot of momentum as it has become increasingly evident that Keytruda is one of the most effective drugs in the field. McDonald's, the iconic fast-food chain, performed well during the Pioneer Fund | Annual Report | 12/31/18 5 period due to great execution of management's franchising plan as well as the ongoing remaking of the company's business, which includes the rollout of its all-day breakfast offerings and some new food items. In addition, McDonald's stores throughout the U.S. are undergoing remodeling and modernization. Finally, strongly positive consumer sentiment throughout most of the period drove a general rally in quick-service restaurants like McDonald's. In financials, CME Group was a strong performer during the period. The company offers many unique interest-rate products, which saw increased volumes due to the rising-rate environment over the past year. CME is also a dominant player within its product universe. We have always liked the stock, and were pleased with its performance during the 12-month period. Finally, tech giant Microsoft has remained a major player in cloud services and continues to expand into the artificial intelligence era, both areas on which we focus in managing the portfolio. The company has a solid balance sheet and good cash flow, and the stock trades at a reasonable valuation. Q Which of your investment decisions detracted from the Fund's benchmark-relative performance during the 12-month period ended December 31, 2018? A Stock selection in communication services was the biggest detractor from the Fund's benchmark-relative performance during the period. A reclassified sector (at the end of September) formerly known as telecommunication services, communication services also pulled in some industry categories from other sectors. For example, media, advertising, broadcasting, cable & satellite, movies and entertainment, and publishing from the consumer discretionary sector, and internet software & services from information technology all moved into the re-classified sector. This was a tricky transaction with regard to weightings, as the portfolio could have been underweight in a particular category before the change, and then suddenly became overweight afterward, and vice versa. The change in sector classification is in the past now, but it did cause a slight hiccup at the time of the phase-in. An underweight to utilities and an overweight to industrials also detracted from the Fund's benchmark-relative returns. Utilities stocks, which have traditionally been viewed as defensive, fared well when the market became very volatile over the final months of the period and equity investors began running for cover. Utilities are interest-rate-sensitive investments, and while we have largely avoided the sector due to high valuations, volatility concerns trumped interest-rate concerns during this particular period, despite rising rates. With regard to industrials, we had a pro-cyclical bias in the portfolio, as we believed the benefits of the December 2017 tax 6 Pioneer Fund | Annual Report | 12/31/18 legislation would continue to drive positive sentiment, and that trade talks between the U.S. and its major trading partners would yield positive results. Industrials is a more cyclical sector, and companies in the cyclical sectors struggled mightily during the market downturn over the final few months of the period. That said, we have maintained the Fund's pro-cyclical bias. Individual positions that detracted from the Fund's benchmark-relative returns during the period included Amazon.com, AT&T, from the new communication services sector, Halliburton, and FedEx. The biggest detractor from benchmark-relative returns during the period was the portfolio's underweight to Amazon versus the S&P 500's weighting. We underweighted Amazon primarily for valuation reasons, but not owning enough Amazon stock hurt relative returns during a period which saw the company continue to perform quite well. The Fund's position in AT&T struggled during the period as the company experienced delays in its long-awaited merger with Time Warner, finally completed it, and then had to deal with the post-merger synergies. There also were issues at DirectTV, an AT&T subsidiary, which hurt the stock's performance. Halliburton was another drag on benchmark-relative performance, as oilfield-services firms struggled at times this year due to volatile energy prices. When oil prices were higher, we had expected there to be more demand for the services companies like Halliburton provide, but the additional demand never materialized. Finally, overnight shipping company FedEx reduced earnings guidance due to some difficulties with integration in the wake of its acquisition of Dutch company TNT two years ago. Slowing economic growth overseas and a prolonged bounce-back from issues concerning a prior-year computer virus also contributed to FedEx's earnings downgrade. Q Could you discuss the Fund's commitment to environmental, social, and governance (ESG) investing? A ESG refers to the three central factors in measuring the sustainability and ethical impact of an investment in a company or business. The Fund has historically followed an ESG-friendly approach. The Fund's portfolio management team uses specific screening criteria to exclude investments in companies that fail to meet certain ESG standards across all industries. Per the prospectus, the Fund will not invest in companies significantly involved in certain business activities, which include, but are not limited to: production of alcohol, tobacco products, certain controversial military weapons, and gambling casinos and other gaming businesses. Pioneer Fund | Annual Report | 12/31/18 7 Q Did the Fund hold any derivatives during the 12-month period ended December 31, 2018? A No. We did not invest in any derivatives during the period. Q What is your outlook for equities as we enter a new calendar and fiscal year? A After the difficult end to the most recent 12-month period, we believe investor and consumer confidence will return as the Fed becomes more data-dependent with regard to future rate moves, rather than just pushing forward with its tightening cycle. That, in turn, should reduce the market's fears of a Fed-induced recession in the U.S. and lead to better performance. We also feel it is in the best interests of the U.S. and China to reach an accommodation on trade. If one is reached, the markets would likely react positively. We are now optimistic about equity valuations, as the recent correction has created more opportunities. We have maintained our pro-cyclical bias in the portfolio, with a heavy focus on future tech. The Fund owns shares of what we believe are high-quality, financially strong, market-leading companies that have been benefiting from their investments in future technologies such as the cloud, internet of things, artificial intelligence, G5, and machine learning. We feel these companies are on the leading edge of major technology trends and improvements that will drive revenues and reduce costs, which may result in faster growth rates and higher profits. In managing the Fund's portfolio, we are always striving to produce a solid risk-adjusted total return, with a strict risk-management discipline, by investing in stocks of high-quality companies that have wide competitive moats around their businesses. Our ESG investment philosophy is a major part of that approach. 8 Pioneer Fund | Annual Report | 12/31/18 Please refer to the Schedule of Investments on pages 18-22 for a full listing of Fund securities. All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. The Fund generally excludes corporate issuers that do not meet or exceed minimum ESG standards. Excluding specific issuers limits the universe of investments available to the Fund, which may mean forgoing some investment opportunities available to funds without similar ESG standards. At times, the Fund's investments may represent industries or industry sectors that are interrelated or have common risks, making it more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. Before investing, consider the product's investment objectives, risks, charges and expenses. Contact your advisor or Amundi Pioneer Asset Management, Inc., for a prospectus or summary prospectus containing this information. Read it carefully. Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund's historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results. Pioneer Fund | Annual Report | 12/31/18 9 Portfolio Summary | 12/31/18 Sector Distribution -------------------------------------------------------------------------------- (As a percentage of total investments)* [THE FOLLOWING DATA WAS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL] Health Care 18.0% Communication Services 15.9% Financials 14.3% Information Technology 13.3% Consumer Discretionary 11.7% Industrials 10.1% Consumer Staples 7.3% Energy 4.1% Materials 2.1% Real Estate 1.2% Government 1.1% Utilities 0.9% 10 Largest Holdings -------------------------------------------------------------------------------- (As a percentage of total investments)* 1. Alphabet, Inc. 4.99% -------------------------------------------------------------------------------- 2. PepsiCo., Inc. 4.57 -------------------------------------------------------------------------------- 3. Home Depot, Inc. 4.54 -------------------------------------------------------------------------------- 4. McDonald's Corp. 4.52 -------------------------------------------------------------------------------- 5. AT&T, Inc. 4.23 -------------------------------------------------------------------------------- 6. Microsoft Corp. 4.04 -------------------------------------------------------------------------------- 7. Facebook, Inc. 3.49 -------------------------------------------------------------------------------- 8. Merck & Co., Inc. 3.29 -------------------------------------------------------------------------------- 9. United Parcel Service, Inc., Class B 3.01 -------------------------------------------------------------------------------- 10. Apple, Inc. 2.98 -------------------------------------------------------------------------------- * Excludes temporary cash investments and all derivative contracts except for options purchased. The Fund is actively managed, and current holdings may be different. The holdings listed should not be considered recommendations to buy or sell any securities listed. 10 Pioneer Fund | Annual Report | 12/31/18 Prices and Distributions | 12/31/18 Net Asset Value per Share -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Class 12/31/18 12/31/17 -------------------------------------------------------------------------------- A $24.76 $28.81 -------------------------------------------------------------------------------- C $21.22 $25.17 -------------------------------------------------------------------------------- R $24.89 $28.93 -------------------------------------------------------------------------------- Y $25.11 $29.17 -------------------------------------------------------------------------------- Distributions per Share: 1/1/18-12/31/18 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Net Investment Short-Term Long-Term Class Income Capital Gains Capital Gains -------------------------------------------------------------------------------- A $0.2846 $0.2107 $3.3114 -------------------------------------------------------------------------------- C $0.0500 $0.2107 $3.3114 -------------------------------------------------------------------------------- R $0.1641 $0.2107 $3.3114 -------------------------------------------------------------------------------- Y $0.3434 $0.2107 $3.3114 -------------------------------------------------------------------------------- Index Definition -------------------------------------------------------------------------------- The Standard & Poor's 500 Index is an unmanaged, commonly used measure of the broad U.S. stock market. Index returns are calculated monthly, assume reinvestment of dividends and, unlike Fund returns, do not reflect any fees, expenses or sales charges. It is not possible to invest directly in an index. The index defined here pertains to the "Value of $10,000 Investment" and "Value of $5 Million Investment" charts on pages 12-15. Pioneer Fund | Annual Report | 12/31/18 11 Performance Update | 12/31/18 Class A Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer Fund at public offering price during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of December 31, 2018) ----------------------------------------------------- Net Public Asset Offering S&P Value Price 500 Period (NAV) (POP) Index ----------------------------------------------------- 10 years 11.23% 10.57% 13.12% 5 years 7.64 6.37 8.49 1 year -1.74 -7.39 -4.38 ----------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2018) ----------------------------------------------------- Gross ----------------------------------------------------- 0.94% ----------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $10,000 Investment Pioneer Fund S&P 500 Index 12/08 $ 9,425 $10,000 12/09 $11,709 $12,646 12/10 $13,549 $14,551 12/11 $12,928 $14,859 12/12 $14,209 $17,237 12/13 $18,906 $22,819 12/14 $20,961 $25,943 12/15 $20,872 $26,302 12/16 $22,875 $29,448 12/17 $27,801 $35,876 12/18 $27,317 $34,303 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. NAV results represent the percent change in net asset value per share. POP returns reflect deduction of maximum 5.75% sales charge. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. Please refer to the financial highlights for a more current expense ratio. 12 Pioneer Fund | Annual Report | 12/31/18 Performance Update | 12/31/18 Class C Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of December 31, 2018) ----------------------------------------------------- S&P If If 500 Period Held Redeemed Index ----------------------------------------------------- 10 years 10.36% 10.36% 13.12% 5 years 6.79 6.79 8.49 1 year -2.52 -2.52 -4.38 ----------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2018) ----------------------------------------------------- Gross ----------------------------------------------------- 1.73% ----------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $10,000 Investment Pioneer Fund S&P 500 Index 12/08 $10,000 $10,000 12/09 $12,328 $12,646 12/10 $14,152 $14,551 12/11 $13,398 $14,859 12/12 $14,613 $17,237 12/13 $19,290 $22,819 12/14 $21,226 $25,943 12/15 $20,965 $26,302 12/16 $22,797 $29,448 12/17 $27,487 $35,876 12/18 $26,795 $34,303 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. Class C shares held for less than one year are also subject to a 1% contingent deferred sales charge (CDSC). "If Held" results represent the percent change in net asset value per share. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. Please refer to the financial highlights for a more current expense ratio. Pioneer Fund | Annual Report | 12/31/18 13 Performance Update | 12/31/18 Class R Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $10,000 investment made in Class R shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of December 31, 2018) ----------------------------------------------------- Net Asset S&P Value 500 Period (NAV) Index ----------------------------------------------------- 10 years 10.84% 13.12% 5 years 7.23 8.49 1 year -2.12 -4.38 ----------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2018) ----------------------------------------------------- Gross ----------------------------------------------------- 1.38% ----------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $10,000 Investment Pioneer Fund S&P 500 Index 12/08 $10,000 $10,000 12/09 $12,394 $12,646 12/10 $14,292 $14,551 12/11 $13,600 $14,859 12/12 $14,901 $17,237 12/13 $19,746 $22,819 12/14 $21,830 $25,943 12/15 $21,663 $26,302 12/16 $23,638 $29,448 12/17 $28,599 $35,876 12/18 $27,994 $34,303 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. Class R shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. Please refer to the financial highlights for a more current expense ratio. 14 Pioneer Fund | Annual Report | 12/31/18 Performance Update | 12/31/18 Class Y Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $5 million investment made in Class Y shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of December 31, 2018) ----------------------------------------------------- Net Asset S&P Value 500 Period (NAV) Index ----------------------------------------------------- 10 years 11.59% 13.12% 5 years 7.92 8.49 1 year -1.56 -4.38 ----------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2018) ----------------------------------------------------- Gross ----------------------------------------------------- 0.69% ----------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $5 Million Investment Pioneer Fund S&P 500 Index 12/08 $ 5,000,000 $ 5,000,000 12/09 $ 6,243,133 $ 6,323,223 12/10 $ 7,252,825 $ 7,275,714 12/11 $ 6,946,966 $ 7,429,362 12/12 $ 7,661,991 $ 8,618,318 12/13 $10,225,556 $11,409,632 12/14 $11,374,337 $12,971,442 12/15 $11,358,126 $13,150,944 12/16 $12,477,735 $14,723,787 12/17 $15,204,324 $17,938,220 12/18 $14,967,165 $17,151,744 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. Class Y shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. Please refer to the financial highlights for a more current expense ratio. Pioneer Fund | Annual Report | 12/31/18 15 Comparing Ongoing Fund Expenses As a shareowner in the Fund, you incur two types of costs: (1) ongoing costs, including management fees, distribution and/or service (12b-1) fees, and other Fund expenses; and (2) transaction costs, including sales charges (loads) on purchase payments. This example is intended to help you understand your ongoing expenses (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds. The example is based on an investment of $1,000 at the beginning of the Fund's latest six-month period and held throughout the six months. Using the Tables -------------------------------------------------------------------------------- Actual Expenses The first table below provides information about actual account values and actual expenses. You may use the information in this table, together with the amount you invested, to estimate the expenses that you paid over the period as follows: (1) Divide your account value by $1,000 Example: an $8,600 account value (divided by) $1,000 = 8.6 (2) Multiply the result in (1) above by the corresponding share class's number in the third row under the heading entitled "Expenses Paid During Period" to estimate the expenses you paid on your account during this period. Expenses Paid on a $1,000 Investment in Pioneer Fund Based on actual returns from July 1, 2018 through December 31, 2018. -------------------------------------------------------------------------------- Share Class A C R Y -------------------------------------------------------------------------------- Beginning Account $1,000.00 $1,000.00 $1,000.00 $1,000.00 Value on 7/1/18 -------------------------------------------------------------------------------- Ending Account $ 965.13 $ 961.44 $ 963.10 $ 966.14 Value on 12/31/18 -------------------------------------------------------------------------------- Expenses Paid $ 4.76 $ 8.70 $ 6.78 $ 3.82 During Period* -------------------------------------------------------------------------------- * Expenses are equal to the Fund's annualized expense ratio of 0.96%, 1.76%, 1.37%, and 0.77%, for Class A, Class C, Class R, and Class Y , respectively, multiplied by the average account value over the period, multiplied by 184/365 (to reflect the one-half year period). 16 Pioneer Fund | Annual Report | 12/31/18 Hypothetical Example for Comparison Purposes The table below provides information about hypothetical account values and hypothetical expenses based on the Fund's actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund's actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds. Please note that the expenses shown in the tables are meant to highlight your ongoing costs only and do not reflect any transaction costs, such as sales charges (loads) that are charged at the time of the transaction. Therefore, the table below is useful in comparing ongoing costs only and will not help you determine the relative total costs of owning different funds. In addition, if these transaction costs were included, your costs would have been higher. Expenses Paid on a $1,000 Investment in Pioneer Fund Based on a hypothetical 5% per year return before expenses, reflecting the period from July 1, 2018 through December 31, 2018. -------------------------------------------------------------------------------- Share Class A C R Y -------------------------------------------------------------------------------- Beginning Account $1,000.00 $1,000.00 $1,000.00 $1,000.00 Value on 7/1/18 -------------------------------------------------------------------------------- Ending Account $1,020.37 $1,016.33 $1,018.30 $1,021.32 Value on 12/31/18 -------------------------------------------------------------------------------- Expenses Paid $ 4.89 $ 8.94 $ 6.97 $ 3.92 During Period* -------------------------------------------------------------------------------- * Expenses are equal to the Fund's annualized expense ratio of 0.96%, 1.76%, 1.37%, and 0.77%, for Class A, Class C, Class R, and Class Y , respectively, multiplied by the average account value over the period, multiplied by 184/365 (to reflect the one-half year period). Pioneer Fund | Annual Report | 12/31/18 17 Schedule of Investments | 12/31/18 ------------------------------------------------------------------------------------------------------------------ Shares Value ------------------------------------------------------------------------------------------------------------------ UNAFFILIATED ISSUERS -- 100.7% COMMON STOCKS -- 99.0% of Net Assets Aerospace & Defense -- 1.9% 538,447 Raytheon Co. $ 82,570,848 -------------- Total Aerospace & Defense $ 82,570,848 ------------------------------------------------------------------------------------------------------------------ Air Freight & Logistics -- 3.0% 1,371,409 United Parcel Service, Inc. $ 133,753,520 -------------- Total Air Freight & Logistics $ 133,753,520 ------------------------------------------------------------------------------------------------------------------ Automobiles -- 0.5% 595,901 Harley-Davidson, Inc. $ 20,332,142 -------------- Total Automobiles $ 20,332,142 ------------------------------------------------------------------------------------------------------------------ Banks -- 5.4% 4,879,166 Bank of America Corp. $ 120,222,650 1,233,838 JPMorgan Chase & Co. 120,447,266 -------------- Total Banks $ 240,669,916 ------------------------------------------------------------------------------------------------------------------ Beverages -- 4.6% 1,839,307 PepsiCo., Inc. $ 203,206,637 -------------- Total Beverages $ 203,206,637 ------------------------------------------------------------------------------------------------------------------ Biotechnology -- 2.2% 510,546 Amgen, Inc. $ 99,387,990 -------------- Total Biotechnology $ 99,387,990 ------------------------------------------------------------------------------------------------------------------ Capital Markets -- 2.8% 60,794 BlackRock, Inc. $ 23,881,099 528,125 CME Group, Inc. 99,350,875 -------------- Total Capital Markets $ 123,231,974 ------------------------------------------------------------------------------------------------------------------ Chemicals -- 2.0% 677,445 International Flavors & Fragrances, Inc. $ 90,960,540 -------------- Total Chemicals $ 90,960,540 ------------------------------------------------------------------------------------------------------------------ Commercial Services & Supplies -- 1.5% 754,319 Waste Management, Inc. $ 67,126,848 -------------- Total Commercial Services & Supplies $ 67,126,848 ------------------------------------------------------------------------------------------------------------------ Communications Equipment -- 0.8% 813,700 Cisco Systems, Inc. $ 35,257,621 -------------- Total Communications Equipment $ 35,257,621 ------------------------------------------------------------------------------------------------------------------ Consumer Finance -- 1.8% 845,536 American Express Co. $ 80,596,492 -------------- Total Consumer Finance $ 80,596,492 ------------------------------------------------------------------------------------------------------------------ The accompanying notes are an integral part of these financial statements. 18 Pioneer Fund | Annual Report | 12/31/18 ------------------------------------------------------------------------------------------------------------------ Shares Value ------------------------------------------------------------------------------------------------------------------ Diversified Financial Services -- 2.5% 68(a) Berkshire Hathaway, Inc., Class A $ 20,808,000 438,411(a) Berkshire Hathaway, Inc., Class B 89,514,758 -------------- Total Diversified Financial Services $ 110,322,758 ------------------------------------------------------------------------------------------------------------------ Diversified Telecommunication Services -- 4.2% 6,589,648 AT&T, Inc. $ 188,068,554 -------------- Total Diversified Telecommunication Services $ 188,068,554 ------------------------------------------------------------------------------------------------------------------ Electric Utilities -- 0.9% 554,000 American Electric Power Co., Inc. $ 41,405,960 -------------- Total Electric Utilities $ 41,405,960 ------------------------------------------------------------------------------------------------------------------ Energy Equipment & Services -- 0.4% 629,593 Halliburton Co. $ 16,734,582 -------------- Total Energy Equipment & Services $ 16,734,582 ------------------------------------------------------------------------------------------------------------------ Entertainment -- 3.2% 317,183(a) Electronic Arts, Inc. $ 25,028,910 1,081,930 Walt Disney Co. 118,633,625 -------------- Total Entertainment $ 143,662,535 ------------------------------------------------------------------------------------------------------------------ Equity Real Estate Investment Trusts (REITs) -- 1.2% 503,772 Crown Castle International Corp. $ 54,724,752 -------------- Total Equity Real Estate Investment Trusts (REITs) $ 54,724,752 ------------------------------------------------------------------------------------------------------------------ Food & Staples Retailing -- 2.1% 447,100 Costco Wholesale Corp. $ 91,078,741 -------------- Total Food & Staples Retailing $ 91,078,741 ------------------------------------------------------------------------------------------------------------------ Food Products -- 0.7% 737,001 Mondelez International, Inc. $ 29,502,150 -------------- Total Food Products $ 29,502,150 ------------------------------------------------------------------------------------------------------------------ Health Care Equipment & Supplies -- 5.0% 918,271 Danaher Corp. $ 94,692,106 1,420,095 Medtronic Plc 129,171,841 -------------- Total Health Care Equipment & Supplies $ 223,863,947 ------------------------------------------------------------------------------------------------------------------ Health Care Providers & Services -- 2.4% 420,651 UnitedHealth Group, Inc. $ 104,792,577 -------------- Total Health Care Providers & Services $ 104,792,577 ------------------------------------------------------------------------------------------------------------------ Hotels, Restaurants & Leisure -- 4.5% 1,131,013 McDonald's Corp. $ 200,833,978 -------------- Total Hotels, Restaurants & Leisure $ 200,833,978 ------------------------------------------------------------------------------------------------------------------ Industrial Conglomerates -- 0.4% 149,558 Honeywell International, Inc. $ 19,759,603 -------------- Total Industrial Conglomerates $ 19,759,603 ------------------------------------------------------------------------------------------------------------------ The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 19 Schedule of Investments | 12/31/18 (continued) ------------------------------------------------------------------------------------------------------------------ Shares Value ------------------------------------------------------------------------------------------------------------------ Insurance -- 1.9% 1,844,942 Hartford Financial Services Group, Inc. $ 82,007,672 -------------- Total Insurance $ 82,007,672 ------------------------------------------------------------------------------------------------------------------ Interactive Media & Services -- 8.5% 212,333(a) Alphabet, Inc. $ 221,879,492 1,182,500(a) Facebook, Inc. 155,013,925 -------------- Total Interactive Media & Services $ 376,893,417 ------------------------------------------------------------------------------------------------------------------ Internet & Direct Marketing Retail -- 2.2% 65,600(a) Amazon.com, Inc. $ 98,529,232 -------------- Total Internet & Direct Marketing Retail $ 98,529,232 ------------------------------------------------------------------------------------------------------------------ IT Services -- 2.8% 952,490 Visa, Inc. $ 125,671,531 -------------- Total IT Services $ 125,671,531 ------------------------------------------------------------------------------------------------------------------ Machinery -- 1.0% 537,684 Lincoln Electric Holdings, Inc. $ 42,396,383 -------------- Total Machinery $ 42,396,383 ------------------------------------------------------------------------------------------------------------------ Metals & Mining -- 0.1% 49,994 Nucor Corp. $ 2,590,189 -------------- Total Metals & Mining $ 2,590,189 ------------------------------------------------------------------------------------------------------------------ Oil, Gas & Consumable Fuels -- 3.7% 767,547 EOG Resources, Inc. $ 66,937,774 1,877,399 TOTAL SA (A.D.R.) 97,962,680 -------------- Total Oil, Gas & Consumable Fuels $ 164,900,454 ------------------------------------------------------------------------------------------------------------------ Pharmaceuticals -- 8.4% 3,865,500(a) Elanco Animal Health, Inc. $ 121,879,215 888,000 Eli Lilly & Co. 102,759,360 1,917,316 Merck & Co., Inc. 146,502,115 -------------- Total Pharmaceuticals $ 371,140,690 ------------------------------------------------------------------------------------------------------------------ Road & Rail -- 2.3% 736,500 Union Pacific Corp. $ 101,806,395 -------------- Total Road & Rail $ 101,806,395 ------------------------------------------------------------------------------------------------------------------ Semiconductors & Semiconductor Equipment -- 2.6% 824,532 Analog Devices, Inc. $ 70,769,582 378,835 Intel Corp. 17,778,726 16,585 Lam Research Corp. 2,258,379 414,201(a) Micron Technology, Inc. 13,142,598 95,636 NVIDIA Corp. 12,767,406 -------------- Total Semiconductors & Semiconductor Equipment $ 116,716,691 ------------------------------------------------------------------------------------------------------------------ The accompanying notes are an integral part of these financial statements. 20 Pioneer Fund | Annual Report | 12/31/18 ------------------------------------------------------------------------------------------------------------------- Shares Value ------------------------------------------------------------------------------------------------------------------- Software -- 4.0% 1,768,478 Microsoft Corp. $ 179,624,310 --------------- Total Software $ 179,624,310 ------------------------------------------------------------------------------------------------------------------- Specialty Retail -- 4.5% 1,175,000 Home Depot, Inc. $ 201,888,500 --------------- Total Specialty Retail $ 201,888,500 ------------------------------------------------------------------------------------------------------------------- Technology Hardware, Storage & Peripherals -- 3.0% 841,000 Apple, Inc. $ 132,659,340 --------------- Total Technology Hardware, Storage & Peripherals $ 132,659,340 ------------------------------------------------------------------------------------------------------------------- TOTAL COMMON STOCKS (Cost $3,877,487,297) $4,398,669,469 ------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------- Principal Amount USD ($) ------------------------------------------------------------------------------------------------------------------- U.S. GOVERNMENT AND AGENCY OBLIGATIONS -- 1.1% of Net Assets 34,860,000(b) U.S. Treasury Bills, 1/15/19 $ 34,831,377 12,790,000(b) U.S. Treasury Bills, 1/24/19 12,772,160 ------------------------------------------------------------------------------------------------------------------- TOTAL U.S. GOVERNMENT AND AGENCY OBLIGATIONS (Cost $47,600,284) $ 47,603,537 ------------------------------------------------------------------------------------------------------------------- TEMPORARY CASH INVESTMENTS -- 0.6% of Net Assets REPURCHASE AGREEMENTS -- 0.6% 16,230,000 $16,230,000 ScotiaBank, 2.92%, dated 12/31/18 plus accrued interest on 1/2/19 collateralized by the following: $5,868,518 Freddie Mac Giant, 3.0% -- 3.5%, 1/1/43 -- 6/1/47 $10,688,767 Federal National Mortgage Association, 2.5% -- 5.0%, 6/1/27 -- 10/1/48. $ 16,230,000 3,915,000 $3,915,000 RBC Capital Markets LLC, 3.00%, dated 12/31/18 plus accrued interest on 1/2/19 collateralized by the following: $593,456 Federal National Mortgage Association, 4.0%, 10/1/48 $3,400,510 Government National Mortgage Association, 5.0%, 11/20/48. 3,915,000 6,885,000 $6,885,000 TD Securities USA LLC, 2.97%, dated 12/31/18 plus accrued interest on 1/2/19 collateralized by $7,022,700 Freddie Mac Giant, 3.5%, 7/1/48. 6,885,000 --------------- $ 27,030,000 ------------------------------------------------------------------------------------------------------------------- TOTAL TEMPORARY CASH INVESTMENTS (Cost $27,030,000) $ 27,030,000 ------------------------------------------------------------------------------------------------------------------- TOTAL INVESTMENTS IN UNAFFILIATED ISSUERS -- 100.7% (Cost $3,952,117,581) $4,473,303,006 ------------------------------------------------------------------------------------------------------------------- OTHER ASSETS AND LIABILITIES -- (0.7)% $ (32,095,722) ------------------------------------------------------------------------------------------------------------------- NET ASSETS -- 100.0% $4,441,207,284 =================================================================================================================== The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 21 Schedule of Investments | 12/31/18 (continued) REIT Real Estate Investment Trust. (A.D.R.) American Depositary Receipts. (a) Non-income producing security. (b) Security issued with a zero coupon. Income is recognized through accretion of discount. Purchases and sales of securities (excluding temporary cash investments) for the year ended December 31, 2018, aggregated 2,885,791,237 and 3,379,084,978, respectively. The Fund is permitted to engage in purchase and sale transactions ("cross trades") with certain funds and accounts for which Amundi Pioneer Asset Management, Inc. (the "Adviser"), serves as the Fund's investment adviser, as set forth in Rule 17a-7 under the Investment Company Act of 1940, pursuant to procedures adopted by the Board of Trustees. Under these procedures, cross trades are affected at current market prices. During the year ended December 31, 2018, the Fund did not engage in cross trade activity. At December 31, 2018, the net unrealized appreciation on investments based on cost for federal tax purposes of $3,960,992,374 was as follows: Aggregate gross unrealized appreciation for all investments in which there is an excess of value over tax cost $ 696,083,631 Aggregate gross unrealized depreciation for all investments in which there is an excess of tax cost over value (183,772,999) ------------- Net unrealized appreciation $ 512,310,632 ============= Various inputs are used in determining the value of the Fund's investments. These inputs are summarized in the three broad levels below. Level 1 - quoted prices in active markets for identical securities. Level 2 - other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.). See Notes to Financial Statements -- Note 1A. Level 3 - significant unobservable inputs (including the Fund's own assumptions in determining fair value of investments). See Notes to Financial Statements -- Note 1A. The following is a summary of the inputs used as of December 31, 2018, in valuing the Fund's investments. -------------------------------------------------------------------------------------------------------- Level 1 Level 2 Level 3 Total -------------------------------------------------------------------------------------------------------- Common Stocks $4,398,669,469 $ -- $ -- $4,398,669,469 U.S. Government and Agency Obligations -- 47,603,537 -- 47,603,537 Repurchase Agreements -- 27,030,000 -- 27,030,000 -------------------------------------------------------------------------------------------------------- Total Investments in Securities $4,398,669,469 $74,633,537 $ -- $4,473,303,006 ======================================================================================================== During the year ended December 31, 2018, there were no transfers between Levels 1, 2 and 3. The accompanying notes are an integral part of these financial statements. 22 Pioneer Fund | Annual Report | 12/31/18 Statement of Assets and Liabilities | 12/31/18 ASSETS: Investments in unaffiliated issuers, at value (cost $3,952,117,581) $4,473,303,006 Cash 9,570,799 Receivables -- Investment securities sold 2,001,485 Fund shares sold 2,334,077 Interest 2,211 Dividend 8,364,352 Other assets 25,507 ------------------------------------------------------------------------------------------------ Total assets $4,495,601,437 ================================================================================================ LIABILITIES: Payables -- Investment securities purchased $ 48,226,987 Fund shares repurchased 4,676,545 Distributions 43,846 Trustees' fees 1,408 Due to affiliates 530,202 Accrued expenses 915,165 ------------------------------------------------------------------------------------------------ Total liabilities $ 54,394,153 ================================================================================================ NET ASSETS: Paid-in capital $3,878,239,357 Distributable earnings 562,967,927 ------------------------------------------------------------------------------------------------ Net assets $4,441,207,284 ================================================================================================ NET ASSET VALUE PER SHARE: No par value (unlimited number of shares authorized) Class A (based on $4,264,175,112/172,220,856 shares) $ 24.76 Class C (based on $37,237,239/1,754,829 shares) $ 21.22 Class R (based on $44,314,373/1,780,558 shares) $ 24.89 Class Y (based on $95,480,560/3,802,049 shares) $ 25.11 MAXIMUM OFFERING PRICE PER SHARE: Class A (based on $24.76 net asset value per share/ 100%-5.75% maximum sales charge) $ 26.27 ================================================================================================ The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 23 Statement of Operations For the Year Ended 12/31/18 INVESTMENT INCOME: Dividends from unaffiliated issuers (net of foreign taxes withheld $1,614,482) $ 94,265,939 Interest from unaffiliated issuers 1,526,299 ------------------------------------------------------------------------------------------------------------------- Total investment income $ 95,792,238 ------------------------------------------------------------------------------------------------------------------- EXPENSES: Management fees Basic fee $ 29,584,098 Performance adjustment (1,920,974) Administrative expense 2,144,547 Transfer agent fees Class A 2,832,609 Class C 81,309 Class R 121,790 Class Y 138,227 Distribution fees Class A 11,778,025 Class C 714,402 Class R 252,584 Shareowner communications expense 1,406,810 Custodian fees 71,584 Registration fees 115,236 Professional fees 226,163 Printing expense 61,139 Trustees' fees 227,600 Insurance expense 47,813 Miscellaneous 104,142 ------------------------------------------------------------------------------------------------------------------- Total expenses $ 47,987,104 ------------------------------------------------------------------------------------------------------------------- Net investment income $ 47,805,134 ------------------------------------------------------------------------------------------------------------------- REALIZED AND UNREALIZED GAIN (LOSS) ON INVESTMENTS: Net realized gain (loss) on: Investments in unaffiliated issuers $ 598,802,823 ------------------------------------------------------------------------------------------------------------------- Change in net unrealized appreciation (depreciation) on: Investments in unaffiliated issuers $(706,609,272) Other assets and liabilities denominated in foreign currencies (8,914) $(706,618,186) ------------------------------------------------------------------------------------------------------------------- Net realized and unrealized gain (loss) on investments $(107,815,363) ------------------------------------------------------------------------------------------------------------------- Net decrease in net assets resulting from operations $ (60,010,229) =================================================================================================================== The accompanying notes are an integral part of these financial statements. 24 Pioneer Fund | Annual Report | 12/31/18 Statements of Changes in Net Assets ------------------------------------------------------------------------------------------------------------ Year Ended Year Ended 12/31/18 12/31/17 ------------------------------------------------------------------------------------------------------------ FROM OPERATIONS: Net investment income (loss) $ 47,805,134 $ 47,553,090 Net realized gain (loss) on investments 598,802,823 742,408,544 Change in net unrealized appreciation (depreciation) on investments (706,618,186) 160,575,603 ------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net assets resulting from operations $ (60,010,229) $ 950,537,237 ------------------------------------------------------------------------------------------------------------ DISTRIBUTIONS TO SHAREOWNERS: Class A ($3.80 and $6.15 per share, respectively) $ (587,620,669) $ (860,536,864)* Class C ($3.57 and $5.93 per share, respectively) (5,447,853) (18,308,271)* Class R ($3.68 and $6.01 per share, respectively) (5,956,040) (9,581,128)* Class Y ($3.86 and $6.22 per share, respectively) (12,568,094) (20,149,327)* ------------------------------------------------------------------------------------------------------------ Total distributions to shareowners $ (611,592,656) $ (908,575,590) ------------------------------------------------------------------------------------------------------------ FROM FUND SHARE TRANSACTIONS: Net proceeds from sales of shares $ 214,238,150 $ 175,645,346 Reinvestment of distributions 586,702,007 867,816,933 Cost of shares repurchased (704,230,996) (768,855,623) ------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net assets resulting from Fund share transactions $ 96,709,161 $ 274,606,656 ------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net assets $ (574,893,724) $ 316,568,303 NET ASSETS:** Beginning of period $5,016,101,008 $4,699,532,705 ------------------------------------------------------------------------------------------------------------ End of period $4,441,207,284 $5,016,101,008 ============================================================================================================ * For the year ended December 31, 2017, distributions to shareowners were presented as follows: Net investment income: Class A ($0.29 per share) $ (43,322,721) Class C ($0.07 per share) (243,794) Class R ($0.15 per share) (256,717) Class Y ($0.36 per share) (1,251,891) Net realized gain: Class A ($5.86 per share) $ (817,214,143) Class C ($5.86 per share) (18,064,477) Class R ($5.86 per share) (9,324,411) Class Y ($5.86 per share) (18,897,436) **For the year ended December 31, 2017, undistributed net investment income was presented as follows: $2,985,264. The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 25 Statements of Changes in Net Assets (continued) ---------------------------------------------------------------------------------------------------------- Year Ended Year Ended Year Ended Year Ended 12/31/18 12/31/18 12/31/17 12/31/17 Shares Amount Shares Amount ---------------------------------------------------------------------------------------------------------- Class A Shares sold 5,351,641 $ 156,601,395 3,912,647 $ 120,647,743 Reinvestment of distributions 21,123,377 566,573,785 29,253,380 828,669,250 Less shares repurchased (19,702,199) (576,987,181) (20,909,923) (650,020,906) ---------------------------------------------------------------------------------------------------------- Net increase 6,772,819 $ 146,187,999 12,256,104 $ 299,296,087 ========================================================================================================== Class C Shares sold 349,800 $ 8,573,741 414,906 $ 11,119,012 Reinvestment of distributions 203,871 4,674,414 616,919 15,213,996 Less shares repurchased (2,361,132) (62,708,192) (1,705,178) (47,007,924) ---------------------------------------------------------------------------------------------------------- Net decrease (1,807,461) $ (49,460,037) (673,353) $ (20,674,916) ========================================================================================================== Class R Shares sold 176,963 $ 5,198,289 204,784 $ 6,550,849 Reinvestment of distributions 219,936 5,920,358 331,928 9,414,736 Less shares repurchased (403,753) (11,885,849) (569,143) (17,415,804) ---------------------------------------------------------------------------------------------------------- Net decrease (6,854) $ (767,202) (32,431) $ (1,450,219) ========================================================================================================== Class Y Shares sold 1,512,961 $ 43,864,725 1,196,411 $ 37,327,742 Reinvestment of distributions 350,419 9,533,450 505,661 14,518,951 Less shares repurchased (1,788,966) (52,649,774) (1,745,383) (54,410,989) ---------------------------------------------------------------------------------------------------------- Net increase (decrease) 74,414 $ 748,401 (43,311) $ (2,564,296) ========================================================================================================== The accompanying notes are an integral part of these financial statements. 26 Pioneer Fund | Annual Report | 12/31/18 Financial Highlights ------------------------------------------------------------------------------------------------------------------------------------ Year Year Year Year Year Ended Ended Ended Ended Ended 12/31/18 12/31/17 12/31/16* 12/31/15* 12/31/14* ------------------------------------------------------------------------------------------------------------------------------------ Class A Net asset value, beginning of period $ 28.81 $ 28.90 $ 31.92 $ 36.67 $ 39.18 ------------------------------------------------------------------------------------------------------------------------------------ Increase (decrease) from investment operations: Net investment income (loss) $ 0.29(a) $ 0.31(a) $ 0.35(a) $ 0.31(a) $ 0.37 Net realized and unrealized gain (loss) on investments (0.54) 5.75 2.56 (0.42) 3.90 ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) from investment operations $ (0.25) $ 6.06 $ 2.91 $ (0.11) $ 4.27 ------------------------------------------------------------------------------------------------------------------------------------ Distributions to shareowners: Net investment income $ (0.28) $ (0.29) $ (0.34) $ (0.30) $ (0.36) Net realized gain (3.52) (5.86) (5.59) (4.34) (6.42) ------------------------------------------------------------------------------------------------------------------------------------ Total distributions $ (3.80) $ (6.15) $ (5.93) $ (4.64) $ (6.78) ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net asset value $ (4.05) $ (0.09) $ (3.02) $ (4.75) $ (2.51) ------------------------------------------------------------------------------------------------------------------------------------ Net asset value, end of period $ 24.76 $ 28.81 $ 28.90 $ 31.92 $ 36.67 ==================================================================================================================================== Total return (b) (1.74)% 21.54%(c) 9.60% (0.43)%(d) 10.86% Ratio of net expenses to average net assets (e) 0.96% 0.94% 0.98% 0.98% 0.96% Ratio of net investment income (loss) to average net assets 0.98% 0.99% 1.09% 0.86% 0.94% Portfolio turnover rate 60% 58% 62% 50% 25% Net assets, end of period (in thousands) $4,264,175 $4,765,993 $4,426,909 $4,402,310 $4,766,086 ==================================================================================================================================== * The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP. (a) The per share data presented above is based on the average shares outstanding for the period presented. (b) Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account. (c) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2017, the total return would have been 21.51%. (d) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.46)%. (e) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00% and 0.00%+, respectively. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 27 Financial Highlights (continued) ------------------------------------------------------------------------------------------------------------------------------------ Year Year Year Year Year Ended Ended Ended Ended Ended 12/31/18 12/31/17 12/31/16* 12/31/15* 12/31/14* ------------------------------------------------------------------------------------------------------------------------------------ Class C Net asset value, beginning of period $ 25.17 $ 25.91 $ 29.20 $ 33.97 $ 36.75 ------------------------------------------------------------------------------------------------------------------------------------ Increase (decrease) from investment operations: Net investment income (loss) $ 0.04(a) $ 0.05(a) $ 0.09(a) $ 0.02(a) $ 0.06 Net realized and unrealized gain (loss) on investments (0.42) 5.14 2.32 0.39) 3.66 ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) from investment operations $ (0.38) $ 5.19 $ 2.41 $ (0.37) $ 3.72 ------------------------------------------------------------------------------------------------------------------------------------ Distributions to shareowners: Net investment income $ (0.05) $ (0.07) $ (0.11) $ (0.06) $ (0.08) Net realized gain (3.52) (5.86) (5.59) (4.34) (6.42) ------------------------------------------------------------------------------------------------------------------------------------ Total distributions $ (3.57) $ (5.93) $ (5.70) $ (4.40) $ (6.50) ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net asset value $ (3.95) $ (0.74) $ (3.29) $ (4.77) $ (2.78) ------------------------------------------------------------------------------------------------------------------------------------ Net asset value, end of period $ 21.22 $ 25.17 $ 25.91 $ 29.20 $ 33.97 ==================================================================================================================================== Total return (b) (2.52)% 20.57% 8.74% (1.23)%(c) 10.04% Ratio of net expenses to average net assets (d) 1.76% 1.73% 1.77% 1.76% 1.73% Ratio of net investment income (loss) to average net assets 0.15% 0.19% 0.30% 0.07% 0.16% Portfolio turnover rate 60% 58% 62% 50% 25% Net assets, end of period (in thousands) $37,237 $89,663 $109,749 $129,720 $160,608 ==================================================================================================================================== * The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP. (a) The per share data presented above is based on the average shares outstanding for the period presented. (b) Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account. (c) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (1.26)%. (d) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%, 0.00%+, respectively. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. 28 Pioneer Fund | Annual Report | 12/31/18 ------------------------------------------------------------------------------------------------------------------------------------ Year Year Year Year Year Ended Ended Ended Ended Ended 12/31/18 12/31/17 12/31/16* 12/31/15* 12/31/14* ------------------------------------------------------------------------------------------------------------------------------------ Class R Net asset value, beginning of period $ 28.93 $ 29.01 $ 32.04 $ 36.80 $ 39.27 ------------------------------------------------------------------------------------------------------------------------------------ Increase (decrease) from investment operations: Net investment income (loss) $ 0.17(a) $ 0.17(a) $ 0.21(a) $ 0.19(a) $ 0.25 Net realized and unrealized gain (loss) on investments (0.53) 5.76 2.57 (0.42) 3.92 ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) from investment operations $ (0.36) $ 5.93 $ 2.78 $ (0.23) $ 4.17 ------------------------------------------------------------------------------------------------------------------------------------ Distributions to shareowners: Net investment income $ (0.16) $ (0.15) $ (0.22) $ (0.19) $ (0.22) Net realized gain (3.52) (5.86) (5.59) (4.34) (6.42) ------------------------------------------------------------------------------------------------------------------------------------ Total distributions $ (3.68) $ (6.01) $ (5.81) $ (4.53) $ (6.64) ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net asset value $ (4.04) $ (0.08) $ (3.03) $ (4.76) $ (2.47) ------------------------------------------------------------------------------------------------------------------------------------ Net asset value, end of period $ 24.89 $ 28.93 $ 29.01 $ 32.04 $ 36.80 ==================================================================================================================================== Total return (b) (2.12)% 20.99% 9.12% (0.77)%(c) 10.56% Ratio of net expenses to average net assets (d) 1.37% 1.38% 1.41% 1.30% 1.27% Ratio of net investment income (loss) to average net assets 0.57% 0.55% 0.66% 0.54% 0.61% Portfolio turnover rate 60% 58% 62% 50% 25% Net assets, end of period (in thousands) $44,314 $51,716 $52,795 $56,380 $66,382 ==================================================================================================================================== * The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP. (a) The per share data presented above is based on the average shares outstanding for the period presented. (b) Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period. (c) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.80)%. (d) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00% and 0.00%+, respectively. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. Pioneer Fund | Annual Report | 12/31/18 29 Financial Highlights (continued) ------------------------------------------------------------------------------------------------------------------------------------ Year Year Year Year Year Ended Ended Ended Ended Ended 12/31/18 12/31/17 12/31/16* 12/31/15* 12/31/14* ------------------------------------------------------------------------------------------------------------------------------------ Class Y Net asset value, beginning of period $ 29.17 $ 29.19 $ 32.18 $ 36.94 $ 39.40 ------------------------------------------------------------------------------------------------------------------------------------ Increase (decrease) from investment operations: Net investment income (loss) $ 0.35(a) $ 0.39(a) $ 0.43(a) $ 0.42(a) $ 0.55 Net realized and unrealized gain (loss) on investments (0.55) 5.81 2.59 (0.43) 3.89 ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) from investment operations $ (0.20) $ 6.20 $ 3.02 $ (0.01) $ 4.44 ------------------------------------------------------------------------------------------------------------------------------------ Distributions to shareowners from: Net investment income $ (0.34) $ (0.36) $ (0.42) $ (0.41) $ (0.48) Net realized gain (3.52) (5.86) (5.59) (4.34) (6.42) ------------------------------------------------------------------------------------------------------------------------------------ Total distributions $ (3.86) $ (6.22) $ (6.01) $ (4.75) $ (6.90) ------------------------------------------------------------------------------------------------------------------------------------ Net increase (decrease) in net asset value $ (4.06) $ (0.02) $ (2.99) $ (4.76) $ (2.46) ------------------------------------------------------------------------------------------------------------------------------------ Net asset value, end of period $ 25.11 $ 29.17 $ 29.19 $ 32.18 $ 36.94 ==================================================================================================================================== Total return (b) (1.56)% 21.85% 9.86% (0.14)%(c) 11.23% Ratio of net expenses to average net assets (d) 0.77% 0.69% 0.73% 0.68% 0.66% Ratio of net investment income (loss) to average net assets 1.17% 1.24% 1.34% 1.14% 1.23% Portfolio turnover rate 60% 58% 62% 50% 25% Net assets, end of period (in thousands) $95,481 $108,729 $110,080 $153,661 $288,846 ==================================================================================================================================== * The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP. (a) The per-share data presented above is based on the average shares outstanding for the period presented. (b) Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period. (c) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.17)%. (d) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00% and 0.00%+, respectively. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. 30 Pioneer Fund | Annual Report | 12/31/18 Notes to Financial Statements | 12/31/18 1. Organization and Significant Accounting Policies Pioneer Fund (the "Fund") is a Delaware statutory trust. The Fund is registered under the Investment Company Act of 1940 as a diversified, open-end management investment company. The investment objective of the Fund is to provide reasonable income and capital growth. The Fund offers six classes of shares designated as Class A, Class C, Class K, Class R, Class T and Class Y shares. Class T and K shares had not commenced operations as of December 31, 2018. Each class of shares represents an interest in the same portfolio of investments of the Fund and has identical rights (based on relative net asset values) to assets and liquidation proceeds. Share classes can bear different rates of class-specific fees and expenses, such as transfer agent and distribution fees. Differences in class-specific fees and expenses will result in differences in net investment income and, therefore, the payment of different dividends from net investment income earned by each class. The Amended and Restated Declaration of Trust of the Fund gives the Board of Trustees the flexibility to specify either per-share voting or dollar-weighted voting when submitting matters for shareowner approval. Under per-share voting, each share of a class of the Fund is entitled to one vote. Under dollar-weighted voting, a shareowner's voting power is determined not by the number of shares owned, but by the dollar value of the shares on the record date. Each share class has exclusive voting rights with respect to matters affecting only that class, including with respect to the distribution plan for that class. There is no distribution plan for Class Y shares. Amundi Pioneer Asset Management, Inc., an indirect wholly owned subsidiary of Amundi and Amundi's wholly owned subsidiary, Amundi USA, Inc., serves as the Fund's investment adviser (the "Adviser"). Amundi Pioneer Distributor, Inc., an affiliate of Amundi Pioneer Asset Management, Inc., serves as the Fund's distributor (the "Distributor"). In August 2018, the Securities and Exchange Commission ("SEC") released a Disclosure Update and Simplification Final Rule. The Final Rule amends Regulation S-X disclosures requirements to conform them to U.S. Generally Accepted Accounting Principles ("U.S. GAAP") for investment companies. The Fund's financial statements were prepared in compliance with the new amendments to Regulation S-X. The Fund is an investment company and follows investment company accounting and reporting guidance under (U.S. GAAP). U.S. GAAP requires the management of the Fund to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets Pioneer Fund | Annual Report | 12/31/18 31 and liabilities at the date of the financial statements, and the reported amounts of income, expenses and gain or loss on investments during the reporting period. Actual results could differ from those estimates. The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements: A. Security Valuation The net asset value of the Fund is computed once daily, on each day the New York Stock Exchange ("NYSE") is open, as of the close of regular trading on the NYSE. Equity securities that have traded on an exchange are valued by using the last sale price on the principal exchange where they are traded. Equity securities that have not traded on the date of valuation, or securities for which sale prices are not available, generally are valued using the mean between the last bid and asked prices or, if both last bid and asked prices are not available, at the last quoted bid price. Last sale and bid and asked prices are provided by independent third party pricing services. In the case of equity securities not traded on an exchange, prices are typically determined by independent third party pricing services using a variety of techniques and methods. The value of foreign securities is translated into U.S. dollars based on foreign currency exchange rate quotations supplied by a third party pricing source. Trading in non-U.S. equity securities is substantially completed each day at various times prior to the close of the NYSE. The values of such securities used in computing the net asset value of the Fund's shares are determined as of such times. The Fund may use a fair value model developed by an independent pricing service to value non-U.S. equity securities. Fixed-income securities are valued by using prices supplied by independent pricing services, which consider such factors as market prices, market events, quotations from one or more brokers, Treasury spreads, yields, maturities and ratings, or may use a pricing matrix or other fair value methods or techniques to provide an estimated value of the security or instrument. A pricing matrix is a means of valuing a debt security on the basis of current market prices for other debt securities, historical trading patterns in the market for fixed-income securities and/or other factors. Non-U.S. debt securities that are listed on an exchange will be valued at the bid price obtained from an independent third party pricing service. When independent third party pricing services are unable to supply prices, or when prices or market quotations are considered to be unreliable, the value of that security may be determined using quotations from one or more broker-dealers. Repurchase agreements are valued at par. Cash may include overnight time deposits at approved financial institutions. 32 Pioneer Fund | Annual Report | 12/31/18 Securities for which independent pricing services or broker-dealers are unable to supply prices or for which market prices and/or quotations are not readily available or are considered to be unreliable are valued by a fair valuation team comprised of certain personnel of the Adviser pursuant to procedures adopted by the Fund's Board of Trustees. The Adviser's fair valuation team uses fair value methods approved by the Valuation Committee of the Board of Trustees. The Adviser's fair valuation team is responsible for monitoring developments that may impact fair valued securities and for discussing and assessing fair values on an ongoing basis, and at least quarterly, with the Valuation Committee of the Board of Trustees. Inputs used when applying fair value methods to value a security may include credit ratings, the financial condition of the company, current market conditions and comparable securities. The Fund may use fair value methods if it is determined that a significant event has occurred after the close of the exchange or market on which the security trades and prior to the determination of the Fund's net asset value. Examples of a significant event might include political or economic news, corporate restructurings, natural disasters, terrorist activity or trading halts. Thus, the valuation of the Fund's securities may differ significantly from exchange prices, and such differences could be material. At December 31, 2018, no securities were valued using fair value methods (other than securities valued using prices supplied by independent pricing services, broker-dealers or using a third party insurance industry pricing model). B. Investment Income and Transactions Dividend income is recorded on the ex-dividend date, except that certain dividends from foreign securities where the ex-dividend date may have passed are recorded as soon as the Fund becomes aware of the ex-dividend data in the exercise of reasonable diligence. Interest income, including interest on income-bearing cash accounts, is recorded on the accrual basis. Dividend and interest income are reported net of unrecoverable foreign taxes withheld at the applicable country rates and net of income accrued on defaulted securities. Interest and dividend income payable by delivery of additional shares is reclassified as PIK (payment-in-kind) income upon receipt and is included in interest and dividend income, respectively. Security transactions are recorded as of trade date. Gains and losses on sales of investments are calculated on the identified cost method for both financial reporting and federal income tax purposes. Pioneer Fund | Annual Report | 12/31/18 33 C. Foreign Currency Translation The books and records of the Fund are maintained in U.S. dollars. Amounts denominated in foreign currencies are translated into U.S. dollars using current exchange rates. Net realized gains and losses on foreign currency transactions, if any, represent, among other things, the net realized gains and losses on foreign currency contracts, disposition of foreign currencies and the difference between the amount of income accrued and the U.S. dollars actually received. Further, the effects of changes in foreign currency exchange rates on investments are not segregated on the Statement of Operations from the effects of changes in the market prices of those securities, but are included with the net realized and unrealized gain or loss on investments. D. Federal Income Taxes It is the Fund's policy to comply with the requirements of the Internal Revenue Code applicable to regulated investment companies and to distribute all of its net taxable income and net realized capital gains, if any, to its shareowners. Therefore, no provision for federal income taxes is required. As of December 31, 2018, the Fund did not accrue any interest or penalties with respect to uncertain tax positions, which, if applicable, would be recorded as an income tax expense on the Statement of Operations. Tax returns filed within the prior three years remain subject to examination by federal and state tax authorities. The amount and character of income and capital gain distributions to shareowners are determined in accordance with federal income tax rules, which may differ from U.S. GAAP. Distributions in excess of net investment income or net realized gains are temporary over distributions for financial statement purposes resulting from differences in the recognition or classification of income or distributions for financial statement and tax purposes. Capital accounts within the financial statements are adjusted for permanent book/tax differences to reflect tax character, but are not adjusted for temporary differences. The Fund has elected to defer $21,486,592 of capital losses recognized between November 1, 2018 through December 31, 2018 to its fiscal year ending December 31, 2019. 34 Pioneer Fund | Annual Report | 12/31/18 The tax character of distributions paid during the years ended December 31, 2018 and December 31, 2017, were as follows: -------------------------------------------------------------------------- 2018 2017 -------------------------------------------------------------------------- Distributions paid from: Ordinary income $ 81,433,923 $152,318,662 Long-term capital gain 530,158,733 756,256,928 -------------------------------------------------------------------------- Total $611,592,656 $908,575,590 ========================================================================== The following shows the components of distributable earnings on a federal income tax basis at December 31, 2018: -------------------------------------------------------------------------- 2018 -------------------------------------------------------------------------- Distributable earnings: Undistributed ordinary income $ 1,961,238 Undistributed long-term capital gain 70,186,255 Current year late year loss (21,486,592) Net unrealized appreciation 512,307,026 -------------------------------------------------------------------------- Total $562,967,927 ========================================================================== The difference between book-basis and tax-basis net unrealized appreciation is attributable to the tax deferral of losses on wash sales and on the tax-basis adjustments on common stocks. E. Fund Shares The Fund records sales and repurchases of its shares as of trade date. The Distributor earned $338,320 in underwriting commissions on the sale of Class A shares during the year ended December 31, 2018. F. Class Allocations Income, common expenses and realized and unrealized gains and losses are calculated at the Fund level and allocated daily to each class of shares based on its respective percentage of adjusted net assets at the beginning of the day. Distribution fees are calculated based on the average daily net asset value attributable to Class A, Class C and Class R shares of the Fund, respectively (see Note 4). Class Y shares do not pay distribution fees. All expenses and fees paid to the Fund's transfer agent for its services are allocated among the classes of shares based on the number of accounts in each class and the ratable allocation of related out-of-pocket expenses (see Note 3). Distributions to shareowners are recorded as of the ex-dividend date. Distributions paid by the Fund with respect to each class of shares are calculated in the same manner and at the same time, except that net investment income dividends to Class A, Class C, Class R and Class Y shares can reflect different transfer agent and distribution expense rates. Pioneer Fund | Annual Report | 12/31/18 35 G. Risks The value of securities held by the Fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political or regulatory conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. At times, the Fund's investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. The Fund's investments in foreign markets and countries with limited developing markets may subject the Fund to a greater degree of risk than investments in a developed market. These risks include disruptive political or economic conditions and the imposition of adverse governmental laws or currency exchange restrictions. With the increased use of technologies such as the Internet to conduct business, the Fund is susceptible to operational, information security and related risks. While the Fund's Adviser has established business continuity plans in the event of, and risk management systems to prevent, limit or mitigate, such cyber-attacks, there are inherent limitations in such plans and systems including the possibility that certain risks have not been identified. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by service providers to the Fund such as Brown Brothers Harriman & Co., the Fund's custodian and accounting agent, and DST Asset Manager Solutions, Inc., the Fund's transfer agent. In addition, many beneficial owners of Fund shares hold them through accounts at broker-dealers, retirement platforms and other financial market participants over which neither the Fund nor Amundi Pioneer exercises control. Each of these may in turn rely on service providers to them, which are also subject to the risk of cyber-attacks. Cybersecurity failures or breaches at Amundi Pioneer or the Fund's service providers or intermediaries have the ability to cause disruptions and impact business operations, potentially resulting in financial losses, interference with the Fund's ability to calculate its net asset value, impediments to trading, the inability of Fund shareowners to effect share purchases, redemptions, or exchanges, or receive distributions, loss of or unauthorized access to private shareowners information and violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, or additional compliance costs. Such costs and losses may not be 36 Pioneer Fund | Annual Report | 12/31/18 covered under any insurance. In addition, maintaining vigilance against cyber-attacks may involve substantial costs over time, and system enhancements may themselves be subject to cyber-attacks. The Fund's prospectus contains unaudited information regarding the Fund's principal risks. Please refer to that document when considering the Fund's principal risks. H. Repurchase Agreements Repurchase agreements are arrangements under which the Fund purchases securities from a broker-dealer or a bank, called the counterparty, upon the agreement of the counterparty to repurchase the securities from the Fund at a later date, and at a specific price, which is typically higher than the purchase price paid by the Fund. The securities purchased serve as the Fund's collateral for the obligation of the counterparty to repurchase the securities. The value of the collateral, including accrued interest, is required to be equal to or in excess of the repurchase price. The collateral for all repurchase agreements is held in safekeeping in the customer-only account of the Fund's custodian or a sub-custodian of the Fund. The Adviser is responsible for determining that the value of the collateral remains at least equal to the repurchase price. In the event of a default by the counterparty, the Fund is entitled to sell the securities, but the Fund may not be able to sell them for the price at which they were purchased, thus causing a loss to the Fund. Additionally, if the counterparty becomes insolvent, there is some risk that the Fund will not have a right to the securities, or the immediate right to sell the securities. Open repurchase agreements as of December 31, 2018 are disclosed in the Fund's Schedule of Investments. 2. Management Agreement The Adviser manages the Fund's portfolio. Management fees are calculated daily at the annual rate of 0.60% of the Fund's average daily net assets up to $7.5 billion, 0.575% on the next $2.5 billion and 0.55% on assets over $10 billion. The basic fee can increase or decrease by a maximum of 0.10% based on the investment performance of the Fund's Class A shares as compared to the Standard and Poor's 500 Index. The performance comparison is made for a rolling 36-month period. In addition, the Adviser, contractually limits any positive adjustment of the Fund's management fee to 0.10% of the Fund's average daily net assets on an annual basis (i.e., to a maximum annual fee of 0.70% after the performance adjustment). For the year ended December 31, 2018, the aggregate performance adjustment resulted in a decrease to the basic fee of $1,920,974. For the year ended December 31, 2018, the net management fee (excluding waivers and/or assumption of expenses) was equivalent to 0.56% of the Fund's average daily net assets. Pioneer Fund | Annual Report | 12/31/18 37 In addition, under the management and administration agreements, certain other services and costs, including accounting, regulatory reporting and insurance premiums, are paid by the Fund as administrative reimbursements. Included in "Due to affiliates" reflected on the Statement of Assets and Liabilities is $321,652 in management fees, administrative costs and certain other reimbursements payable to the Adviser at December 31, 2018. 3. Transfer Agent DST Asset Manager Solutions, Inc. serves as the transfer agent to the Fund at negotiated rates. Transfer agent fees and payables shown on the Statement of Operations and the Statement of Assets and Liabilities, respectively, include sub-transfer agent expenses incurred through the Fund's omnibus relationship contracts. In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses incurred by the transfer agent related to shareholder communications activities such as proxy and statement mailings and outgoing phone calls. For the year ended December 31, 2018, such out-of-pocket expenses by class of shares were as follows: -------------------------------------------------------------------------------- Shareowner Communications: -------------------------------------------------------------------------------- Class A $1,381,203 Class C 18,990 Class R 2,960 Class Y 3,657 -------------------------------------------------------------------------------- Total $1,406,810 ================================================================================ 4. Distribution and Service Plans The Fund has adopted a distribution plan (the "Plan") pursuant to Rule 12b-1 of the Investment Company Act of 1940 with respect to its Class A, Class C and Class R shares. Pursuant to the Plan, the Fund pays the Distributor 0.25% of the average daily net assets attributable to Class A shares as compensation for personal services and/or account maintenance services or distribution services with regard to Class A shares. Pursuant to the Plan, the Fund also pays the Distributor 1.00% of the average daily net assets attributable to Class C shares. The fee for Class C shares consists of a 0.25% service fee and a 0.75% distribution fee paid as compensation for personal services and/or account maintenance services or distribution services with regard to Class C shares. Pursuant to the Plan, the Fund further pays the Distributor 0.50% of the average daily net assets attributable to Class R shares for distribution services. Included in "Due to affiliates" reflected on the Statement of Assets and Liabilities is $208,550 in distribution fees payable to the Distributor at December 31, 2018. 38 Pioneer Fund | Annual Report | 12/31/18 The Fund also has adopted a separate service plan for Class R shares (the "Service Plan"). The Service Plan authorizes the Fund to pay securities dealers, plan administrators or other service organizations that agree to provide certain services to retirement plans or plan participants holding shares of the Fund a service fee of up to 0.25% of the Fund's average daily net assets attributable to Class R shares held by such plans. In addition, redemptions of each class of shares (except Class R and Class Y shares) may be subject to a contingent deferred sales charge ("CDSC"). A CDSC of 1.00% may be imposed on redemptions of certain net asset value purchases of Class A shares within 12 months of purchase. Redemptions of Class C shares within 12 months of purchase are subject to a CDSC of 1.00%, based on the lower of cost or market value of shares being redeemed. Shares purchased as part of an exchange remain subject to any CDSC that applied to the original purchase of those shares. There is no CDSC for Class R or Class Y shares. Proceeds from the CDSCs are paid to the Distributor. For the year ended December 31, 2018, CDSCs in the amount of $5,012 were paid to the Distributor. 5. Line of Credit Facility The Fund, along with certain other funds in the Pioneer Family of Funds (the "Funds"), participates in a committed, unsecured revolving line of credit facility. Borrowings are used solely for temporary or emergency purposes. The Fund may borrow up to the lesser of the amount available under the facility or the limits set for borrowing by the Fund's prospectus and the 1940 Act. Prior to August 1, 2018, the credit facility was in the amount of $195 million. Effective August 1, 2018, the Fund participates in credit facility that is in the amount of $250 million. Under such credit facility, depending on the type of loan, interest on borrowings is payable at the London Interbank Offered Rate ("LIBOR") plus 0.90% on an annualized basis, or the Alternate Base Rate, which is the greater of (a) the facility's administrative agent's daily announced prime rate on the borrowing date, (b) 2% plus the Federal Funds Rate on the borrowing date or (c) 2% plus the overnight Eurodollar rate on the borrowing date. The Funds pay an annual commitment fee to participate in a credit facility. The commitment fee is allocated among participating Funds based on an allocation schedule set forth in the credit agreement. For the year ended December 31, 2018, the Fund had no borrowings under the credit facility. Pioneer Fund | Annual Report | 12/31/18 39 Report of Independent Registered Public Accounting Firm To the Board of Trustees and the Shareholders of Pioneer Fund: -------------------------------------------------------------------------------- Opinion on the Financial Statements We have audited the accompanying statement of assets and liabilities of Pioneer Fund (the "Fund"), including the schedule of investments, as of December 31, 2018, and the related statements of operations, changes in net assets and the financial highlights for the year then ended and the related notes, and the statement of changes in net assets and financial highlights for the year ended December 31, 2017 (collectively referred to as the "financial statements"). The financial highlights for the periods ended December 31, 2014, December 31, 2015 and December 31, 2016 were audited by another independent registered public accounting firm whose report, dated February 22, 2017, expressed an unqualified opinion on those financial highlights. In our opinion, the financial statements present fairly, in all material respects, the financial position of Pioneer Fund at December 31, 2018, the results of its operations, the changes in its nets assets, and the financial highlights for the year ended, and the statement of changes in net assets and the financial highlights for the year ended December 31, 2017, in conformity with U.S. generally accepted accounting principles. Basis for Opinion These financial statements are the responsibility of the Fund's management. Our responsibility is to express an opinion on the Fund's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Fund is not required to have, nor were we engaged to perform, an audit of the Fund's internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting, but not for the purpose of expressing an opinion on the effectiveness of the Fund's internal control over financial reporting. Accordingly, we express no such opinion. 40 Pioneer Fund | Annual Report | 12/31/18 Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our procedures included confirmation of securities owned as of December 31, 2018, by correspondence with the custodian and brokers. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. /s/ Ernst & Young LLP We have served as the Fund's auditor since 2017. Boston, Massachusetts February 27, 2019 Pioneer Fund | Annual Report | 12/31/18 41 ADDITIONAL INFORMATION For the year ended December 31, 2018, certain dividends paid by the Fund may be subject to a maximum tax rate of 15%, as provided for by the Jobs and Growth Tax Relief Reconciliation Act (the Act) of 2003. The Fund intends to designate up to the maximum amount of such dividends allowable under the Act, as taxed at a maximum rate of 15%. Complete information will be computed and reported in conjunction with your 2018 form 1099-DIV. The qualifying percentage of the Fund's ordinary income dividends for the purpose of the corporate dividends received deduction was 100.00% . The percentages of the Fund's ordinary income distributions that are exempt from nonresident alien (NRA) tax withholding resulting from qualified short term gains were 41.77%. Change in Independent Registered Public Accounting Firm Prior to July 3, 2017 Pioneer Investment Management, Inc. (the "Adviser"), the Fund's investment adviser, was an indirect, wholly owned subsidiary of UniCredit S.p.A. ("UniCredit"). On that date, UniCredit completed the sale of its Pioneer Investments business, which includes the Adviser, to Amundi (the "Transaction"). As a result of the Transaction, the Adviser became an indirect, wholly owned subsidiary of Amundi. Amundi is controlled by Credit Agricole S.A. Amundi is headquartered in Paris, France, and, as of September 30, 2016, had more than $1.1 trillion in assets under management worldwide. Deloitte & Touche LLP ("D&T"), the Fund's previous independent registered public accounting firm, informed the Audit Committee and the Board that it would no longer be independent with respect to the Fund upon the completion of the Transaction as a result of certain services being provided to Amundi and Credit Agricole, and, accordingly, that it intended to resign as the Fund's independent registered public accounting firm upon the completion of the Transaction. D&T's resignation was effective on July 3, 2017, when the Transaction was completed. During the periods as to which D&T has served as the Fund's independent registered public accounting firm, including the Fund's two most recent fiscal years, D&T's reports on the Fund's financial statements have not contained an adverse opinion or disclaimer of opinion and have not been qualified or modified as to uncertainty, audit scope or accounting principles. Further, there have been no disagreements with D&T on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which, if not resolved to the satisfaction of D&T, would have caused D&T to make reference to the subject matter of the disagreement in connection with its report on the financial statements. In addition, there have been no reportable events of the kind described in Item 304(a)(1)(v) of Regulation S-K under the Securities Exchange Act of 1934. 42 Pioneer Fund | Annual Report | 12/31/18 Effective immediately following the completion of the Transaction on July 3, 2017, the Board, acting upon the recommendation of the Audit Committee, engaged a new independent registered public accounting firm, Ernst & Young LLP ("EY"), for the Fund's fiscal year ended December 31, 2017. Prior to its engagement, EY had advised the Fund's Audit Committee that EY had identified the following matters, in each case relating to services rendered by other member firms of Ernst & Young Global Limited, all of which are located outside the United States, to UniCredit and certain of its subsidiaries during the period commencing July 1, 2016, that it determined to be inconsistent with the auditor independence rules set forth by the Securities and Exchange Commission ("SEC"): (a) project management support services to UniCredit in the Czech Republic, Germany, Italy, Serbia and Slovenia in relation to twenty-two projects, that were determined to be inconsistent with Rule 2-01(c)(4)(vi) of Regulation S-X (management functions); (b) two engagements for UniCredit in Italy where fees were contingent/success based and that were determined to be inconsistent with Rule 2-01(c)(5) of Regulation S-X (contingent fees); (c) four engagements where legal and expert services were provided to UniCredit in the Czech Republic and Germany, and twenty engagements where the legal advisory services were provided to UniCredit in Austria, Czech Republic, Italy and Poland, that were determined to be inconsistent with Rule 2-01(c)(4)(ix) and (x) of Regulation S-X (legal and expert services); and (d) two engagements for UniCredit in Italy involving assistance in the sale of certain assets, that were determined to be inconsistent with Rule 2-01(c)(4)(viii) of Regulation S-X (broker-dealer, investment adviser or investment banking services). None of the foregoing services involved the Fund, any of the other funds in the Pioneer Family of Funds or any other Pioneer entity sold by UniCredit in the Transaction. EY advised the Audit Committee that it had considered the matters described above and had concluded that such matters would not impair EY's ability to exercise objective and impartial judgment in connection with the audits of the financial statements of the Fund under the SEC and Public Company Accounting Oversight Board independence rules, and that a reasonable investor with knowledge of all relevant facts and circumstances would reach the same conclusion. Management and the Audit Committee considered these matters and discussed the matters with EY and, based upon EY's description of the matters and statements made by EY, Management and the Audit Committee believe that EY will be capable of exercising objective and impartial judgment in connection with the audits of the financial statements of the Fund, and Management further believes that a reasonable investor with knowledge of all relevant facts and circumstances would reach the same conclusion. Pioneer Fund | Annual Report | 12/31/18 43 Approval of Investment Management Agreement Amundi Pioneer Asset Management, Inc. ("APAM") serves as the investment adviser to Pioneer Fund (the "Fund") pursuant to an investment management agreement between APAM and the Fund. In order for APAM to remain the investment adviser of the Fund, the Trustees of the Fund must determine annually whether to renew the investment management agreement for the Fund. The contract review process began in January 2018 as the Trustees of the Fund agreed on, among other things, an overall approach and timeline for the process. Contract review materials were provided to the Trustees in March 2018, July 2018 and September 2018. In addition, the Trustees reviewed and discussed the Fund's performance at regularly scheduled meetings throughout the year, and took into account other information related to the Fund provided to the Trustees at regularly scheduled meetings, in connection with the review of the Fund's investment management agreement. In March 2018, the Trustees, among other things, discussed the memorandum provided by Fund counsel that summarized the legal standards and other considerations that are relevant to the Trustees in their deliberations regarding the renewal of the investment management agreement, and reviewed and discussed the qualifications of the investment management teams for the Fund, as well as the level of investment by the Fund's portfolio managers in the Fund. In July 2018, the Trustees, among other things, reviewed the Fund's management fees and total expense ratios, the financial statements of APAM and its parent companies, profitability analyses provided by APAM, and analyses from APAM as to possible economies of scale. The Trustees also reviewed the profitability of the institutional business of APAM and APAM's affiliate, Amundi Pioneer Institutional Asset Management, Inc. ("APIAM" and, together with APAM, "Amundi Pioneer"), as compared to that of APAM's fund management business, and considered the differences between the fees and expenses of the Fund and the fees and expenses of APAM's and APIAM's institutional accounts, as well as the different services provided by APAM to the Fund and by APAM and APIAM to the institutional accounts. The Trustees further considered contract review materials, including additional materials received in response to the Trustees' request, in September 2018. At a meeting held on September 18, 2018, based on their evaluation of the information provided by APAM and third parties, the Trustees of the Fund, including the Independent Trustees voting separately, unanimously approved the renewal of the investment management agreement for another year. In approving the renewal of the investment management agreement, the Trustees 44 Pioneer Fund | Annual Report | 12/31/18 considered various factors that they determined were relevant, including the factors described below. The Trustees did not identify any single factor as the controlling factor in determining to approve the renewal of the agreement. Nature, Extent and Quality of Services The Trustees considered the nature, extent and quality of the services that had been provided by APAM to the Fund, taking into account the investment objective and strategy of the Fund. The Trustees also reviewed APAM's investment approach for the Fund and its research process. The Trustees considered the resources of APAM and the personnel of APAM who provide investment management services to the Fund. They also reviewed the amount of non-Fund assets managed by the portfolio managers of the Fund. They considered the non-investment resources and personnel of APAM that are involved in APAM's services to the Fund, including APAM's compliance, risk management, and legal resources and personnel. The Trustees noted the substantial attention and high priority given by APAM's senior management to the Pioneer Fund complex. The Trustees considered that APAM supervises and monitors the performance of the Fund's service providers and provides the Fund with personnel (including Fund officers) and other resources that are necessary for the Fund's business management and operations. The Trustees also considered that, as administrator, APAM is responsible for the administration of the Fund's business and other affairs. The Trustees considered the fees paid to APAM for the provision of administration services. Based on these considerations, the Trustees concluded that the nature, extent and quality of services that had been provided by APAM to the Fund were satisfactory and consistent with the terms of the investment management agreement. Performance of the Fund In considering the Fund's performance, the Trustees regularly review and discuss throughout the year data prepared by APAM and information comparing the Fund's performance with the performance of its peer group of funds, as classified by Morningstar, Inc. (Morningstar), and the performance of the Fund's benchmark index. They also discuss the Fund's performance with APAM on a regular basis. The Trustees' regular reviews and discussions were factored into the Trustees' deliberations concerning the renewal of the investment management agreement. Pioneer Fund | Annual Report | 12/31/18 45 Management Fee and Expenses The Trustees considered information showing the fees and expenses of the Fund in comparison to the management fees of its peer group of funds as classified by Morningstar and also to the expense ratios of a peer group of funds selected on the basis of criteria determined by the Independent Trustees for this purpose using data provided by Strategic Insight Mutual Fund Research and Consulting, LLC (Strategic Insight), an independent third party. The peer group comparisons referred to below are organized in quintiles. Each quintile represents one-fifth of the peer group. In all peer group comparisons referred to below, first quintile is most favorable to the Fund's shareowners. The Trustees noted that they separately review and consider the impact of the Fund's transfer agency and Fund- and APAM-paid expenses for sub-transfer agency and intermediary arrangements, and that the results of the most recent such review were considered in the consideration of the Fund's expense ratio. The Trustees considered that the Fund's management fee for the most recent fiscal year was in the second quintile relative to the management fees paid by other funds in its Morningstar category for the comparable period. The Trustees noted the impact of the Fund's performance on the management fee paid by the Fund. The Trustees considered that the expense ratio of the Fund's Class A shares for the most recent fiscal year was in the second quintile relative to its Strategic Insight peer group for the comparable period. The Trustees reviewed management fees charged by APAM and APIAM to institutional and other clients, including publicly offered European funds sponsored by APAM's affiliates, unaffiliated U.S. registered investment companies (in a sub-advisory capacity), and unaffiliated foreign and domestic separate accounts. The Trustees also considered APAM's costs in providing services to the Fund and APAM's and APIAM's costs in providing services to the other clients and considered the differences in management fees and profit margins for fund and non-fund services. In evaluating the fees associated with APAM's and APIAM's client accounts, the Trustees took into account the respective demands, resources and complexity associated with the Fund and other client accounts. The Trustees noted that, in some instances, the fee rates for those clients were lower than the management fee for the Fund and considered that, under the investment management agreement with the Fund, APAM performs additional services for the Fund that it does not provide to those other clients or services that are broader in scope, including oversight of the Fund's other service providers and activities related to compliance and the extensive regulatory and tax regimes to which the Fund is subject. The Trustees also considered the entrepreneurial risks associated with APAM's management of the Fund. 46 Pioneer Fund | Annual Report | 12/31/18 The Trustees concluded that the management fee payable by the Fund to APAM was reasonable in relation to the nature and quality of the services provided by APAM. Profitability The Trustees considered information provided by APAM regarding the profitability of APAM with respect to the advisory services provided by APAM to the Fund, including the methodology used by APAM in allocating certain of its costs to the management of the Fund. The Trustees also considered APAM's profit margin in connection with the overall operation of the Fund. They further reviewed the financial results, including the profit margins, realized by APAM and APIAM from non-fund businesses. The Trustees considered APAM's profit margins in comparison to the limited industry data available and noted that the profitability of any adviser was affected by numerous factors, including its organizational structure and method for allocating expenses. The Trustees concluded that APAM's profitability with respect to the management of the Fund was not unreasonable. Economies of Scale The Trustees considered APAM's views relating to economies of scale in connection with the Pioneer Funds as fund assets grow and the extent to which any such economies of scale are shared with the Fund and Fund shareholders. The Trustees recognize that economies of scale are difficult to identify and quantify, and that, among other factors that may be relevant, are the following: fee levels, expense subsidization, investment by APAM in research and analytical capabilities and APAM's commitment and resource allocation to the Fund. The Trustees noted that profitability also may be an indicator of the availability of any economies of scale, although profitability may vary for other reasons including due to reductions in expenses. The Trustees concluded that economies of scale, if any, were being appropriately shared with the Fund. Other Benefits The Trustees considered the other benefits that APAM enjoys from its relationship with the Fund. The Trustees considered the character and amount of fees paid or to be paid by the Fund, other than under the investment management agreement, for services provided by APAM and its affiliates. The Trustees further considered the revenues and profitability of APAM's businesses other than the Fund business. To the extent applicable, the Trustees also considered the benefits to the Fund and to APAM and its affiliates from the use of "soft" commission dollars generated by the Fund to pay for research and brokerage services. Pioneer Fund | Annual Report | 12/31/18 47 The Trustees considered that Amundi Pioneer is the principal U.S. asset management business of Amundi, which is one of the largest asset managers globally. Amundi's worldwide asset management business manages over $1.7 trillion in assets (including the Pioneer Funds). The Trustees considered that APAM's relationship with Amundi creates potential opportunities for APAM, APIAM and Amundi that derive from APAM's relationships with the Fund, including Amundi's ability to market the services of APAM globally. The Trustees noted that APAM has access to additional research and portfolio management capabilities as a result of its relationship with Amundi and Amundi's enhanced global presence that may contribute to an increase in the resources available to APAM. The Trustees considered that APAM and the Fund receive reciprocal intangible benefits from the relationship, including mutual brand recognition and, for the Fund, direct and indirect access to the resources of a large global asset manager. The Trustees concluded that any such benefits received by APAM as a result of its relationship with the Fund were reasonable. Conclusion After consideration of the factors described above as well as other factors, the Trustees, including the Independent Trustees, concluded that the investment management agreement for the Fund, including the fees payable thereunder, was fair and reasonable and voted to approve the proposed renewal of the investment management agreement. 48 Pioneer Fund | Annual Report | 12/31/18 Trustees, Officers and Service Providers Investment Adviser Amundi Pioneer Asset Management, Inc. Custodian and Sub-Administrator Brown Brothers Harriman & Co. Independent Registered Public Accounting Firm Ernst & Young LLP Principal Underwriter Amundi Pioneer Distributor, Inc. Legal Counsel Morgan, Lewis & Bockius LLP Shareowner Services and Transfer Agent DST Asset Manager Solutions, Inc. Proxy Voting Policies and Procedures of the Fund are available without charge, upon request, by calling our toll free number (1-800-225-6292). Information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is publicly available to shareowners at www.amundipioneer.com. This information is also available on the Securities and Exchange Commission's web site at www.sec.gov. Trustees and Officers The Fund's Trustees and officers are listed below, together with their principal occupations and other directorships they have held during at least the past five years. Trustees who are interested persons of the Fund within the meaning of the 1940 Act are referred to as Interested Trustees. Trustees who are not interested persons of the Fund are referred to as Independent Trustees. Each of the Trustees serves as a Trustee of each of the 43 U.S. registered investment portfolios for which Amundi Pioneer serves as investment adviser (the "Pioneer Funds"). The address for all Trustees and all officers of the Fund is 60 State Street, Boston, Massachusetts 02109. The Statement of Additional Information of the Fund includes additional information about the Trustees and is available, without charge, upon request, by calling 1-800-225-6292. Pioneer Fund | Annual Report | 12/31/18 49 Independent Trustees ------------------------------------------------------------------------------------------------------------------------------------ Name, Age and Position Term of Office and Other Directorships Held With the Fund Length of Service Principal Occupation Held by Trustee ------------------------------------------------------------------------------------------------------------------------------------ Thomas J. Perna (68) Trustee since 2006. Private investor (2004 - 2008 and 2013 - present); Director, Broadridge Financial Chairman of the Board Serves until a Chairman (2008 - 2013) and Chief Executive Officer Solutions, Inc. (investor and Trustee successor trustee is (2008 - 2012), Quadriserv, Inc. (technology communications and securities elected or earlier products for securities lending industry); and processing provider for retirement Senior Executive Vice President, The Bank of New financial services industry) or removal. York (financial and securities services) (2009 - present); Director, (1986 - 2004) Quadriserv, Inc. (2005 - 2013); and Commissioner, New Jersey State Civil Service Commission (2011 - 2015) ------------------------------------------------------------------------------------------------------------------------------------ David R. Bock (75) Trustee since 2005. Managing Partner, Federal City Capital Advisors Director of New York Mortgage Trustee Serves until a (corporate advisory services company) (1997 - Trust (publicly-traded successor trustee 2004 and 2008 - present); Interim Chief Executive mortgage REIT) (2004 - 2009, is elected or Officer, Oxford Analytica, Inc. (privately held 2012 - present); Director of earlier retirement research and consulting company) (2010); The Swiss Helvetia Fund, Inc. or removal. Executive Vice President and Chief Financial (closed-end fund) (2010 - Officer, I-trax, Inc. (publicly traded health 2017); Director of Oxford care services company) (2004 - 2007); and Analytica, Inc. (2008 - Executive Vice President and Chief Financial 2015); and Director of Officer, Pedestal Inc. (internet-based mortgage Enterprise Community trading company) (2000 - 2002); Private Investment, Inc. (privately- Consultant (1995 - 1997); Managing Director, held affordable housing Lehman Brothers (1992 - 1995); and Executive, The finance company) (1985 - 2010) World Bank (1979 - 1992) ------------------------------------------------------------------------------------------------------------------------------------ Benjamin M. Friedman (74) Trustee since 2008. William Joseph Maier Professor of Political Trustee, Mellon Institutional Trustee Serves until a Economy, Harvard University (1972 - present) Funds Investment Trust and successor trustee Mellon Institutional Funds is elected or Master Portfolio (oversaw 17 earlier retirement portfolios in fund complex) or removal. (1989 - 2008) ------------------------------------------------------------------------------------------------------------------------------------ 50 Pioneer Fund | Annual Report | 12/31/18 ------------------------------------------------------------------------------------------------------------------------------------ Name, Age and Position Term of Office and Other Directorships Held With the Fund Length of Service Principal Occupation Held by Trustee ------------------------------------------------------------------------------------------------------------------------------------ Margaret B.W. Graham (71) Trustee since 1990. Founding Director, Vice-President and Corporate None Trustee Serves until a Secretary, The Winthrop Group, Inc. (consulting successor trustee firm) (1982 - present); Desautels Faculty of is elected or Management, McGill University (1999 - 2017); and earlier retirement Manager of Research Operations and Organizational or removal. Learning, Xerox PARC, Xerox's advance research center (1990-1994) ------------------------------------------------------------------------------------------------------------------------------------ Lorraine H. Monchak (62) Trustee since 2017. Chief Investment Officer, 1199 SEIU Funds None Trustee (Advisory Trustee (healthcare workers union pension funds) (2001 - from 2014 - 2017) present); Vice President - International Serves until a Investments Group, American International Group, successor trustee Inc. (insurance company) (1993 - 2001); Vice is elected or President - Corporate Finance and Treasury Group, earlier retirement Citibank, N.A. (1980 - 1986 and 1990 - 1993); or removal. Vice President - Asset/Liability Management Group, Federal Farm Funding Corporation (government-sponsored issuer of debt securities) (1988 - 1990); Mortgage Strategies Group, Shearson Lehman Hutton, Inc. (investment bank) (1987 - 1988); and Mortgage Strategies Group, Drexel Burnham Lambert, Ltd. (investment bank) (1986 - 1987) ------------------------------------------------------------------------------------------------------------------------------------ Marguerite A. Piret (70) Trustee since 1982. President and Chief Executive Officer, Newbury Director of New America High Trustee Serves until a Piret Company (investment banking firm) (1981 - Income Fund, Inc. successor trustee present) (closed-end investment is elected or company) (2004 - present); earlier retirement and Member, Board of or removal. Governors, Investment Company Institute (2000 - 2006) ------------------------------------------------------------------------------------------------------------------------------------ Fred J. Ricciardi (71) Trustee since 2014. Consultant (investment company services) (2012 - None Trustee Serves until a present); Executive Vice President, BNY Mellon successor trustee (financial and investment company services) is elected or (1969 - 2012); Director, BNY International earlier retirement Financing Corp. (financial services) (2002 - or removal. 2012); and Director, Mellon Overseas Investment Corp. (financial services) (2009 - 2012); Director, Financial Models (technology) (2005 - 2007); Director, BNY Hamilton Funds, Ireland (offshore investment companies) (2004 - 2007); Chairman/Director, AIB/BNY Securities Services Ltd., Ireland (financial services) (1999 - 2006); and Chairman, BNY Alternative Investment Services, Inc. (financial services) (2005 - 2007) ------------------------------------------------------------------------------------------------------------------------------------ Pioneer Fund | Annual Report | 12/31/18 51 Interested Trustees ------------------------------------------------------------------------------------------------------------------------------------ Name, Age and Position Term of Office and Other Directorships Held With the Fund Length of Service Principal Occupation Held by Trustee ------------------------------------------------------------------------------------------------------------------------------------ Lisa M. Jones (56)* Trustee since 2017. Director, CEO and President of Amundi Pioneer None Trustee, President Serves until a Asset Management USA, Inc. (since September 2014); and Chief Executive successor trustee Director, CEO and President of Amundi Pioneer Officer is elected or Asset Management, Inc. (since September 2014); earlier retirement Director, CEO and President of Amundi Pioneer or removal Distributor, Inc. (since September 2014); Director, CEO and President of Amundi Pioneer Institutional Asset Management, Inc. (since September 2014); Chair, Amundi Pioneer Asset Management USA, Inc., Amundi Pioneer Distributor, Inc. and Amundi Pioneer Institutional Asset Management, Inc. (September 2014 - 2018); Managing Director, Morgan Stanley Investment Management (2010 - 2013); and Director of Institutional Business, CEO of International, Eaton Vance Management (2005 - 2010) ------------------------------------------------------------------------------------------------------------------------------------ Kenneth J. Taubes (60)* Trustee since 2014. Director and Executive Vice President (since 2008) None Trustee Serves until a and Chief Investment Officer, U.S. (since 2010) successor trustee of Amundi Pioneer Asset Management USA, Inc.; is elected or Executive Vice President and Chief Investment earlier retirement Officer, U.S. of Amundi Pioneer (since 2008); or removal Executive Vice President of Amundi Pioneer Institutional Asset Management, Inc. (since 2009); and Portfolio Manager of Amundi Pioneer (since 1999) ------------------------------------------------------------------------------------------------------------------------------------ * Ms. Jones and Mr. Taubes are Interested Trustees because they are officers or directors of the Fund's investment adviser and certain of its affiliates. 52 Pioneer Fund | Annual Report | 12/31/18 Fund Officers ------------------------------------------------------------------------------------------------------------------------------------ Name, Age and Position Term of Office and Other Directorships Held With the Fund Length of Service Principal Occupation Held by Officer ------------------------------------------------------------------------------------------------------------------------------------ Christopher J. Kelley (54) Since 2003. Serves Vice President and Associate General Counsel of None Secretary and Chief at the discretion Amundi Pioneer since January 2008; Secretary and Legal Officer of the Board Chief Legal Officer of all of the Pioneer Funds since June 2010; Assistant Secretary of all of the Pioneer Funds from September 2003 to May 2010; and Vice President and Senior Counsel of Amundi Pioneer from July 2002 to December 2007 ------------------------------------------------------------------------------------------------------------------------------------ Carol B. Hannigan (57) Since 2010. Serves Fund Governance Director of Amundi Pioneer since None Assistant Secretary at the discretion December 2006 and Assistant Secretary of all the of the Board Pioneer Funds since June 2010; Manager - Fund Governance of Amundi Pioneer from December 2003 to November 2006; and Senior Paralegal of Amundi Pioneer from January 2000 to November 2003 ------------------------------------------------------------------------------------------------------------------------------------ Thomas Reyes (56) Since 2010. Serves Senior Counsel of Amundi Pioneer since May 2013 None Assistant Secretary at the discretion and Assistant Secretary of all the Pioneer Funds of the Board since June 2010; and Counsel of Amundi Pioneer from June 2007 to May 2013 ------------------------------------------------------------------------------------------------------------------------------------ Mark E. Bradley (59) Since 2008. Serves Vice President - Fund Treasury of Amundi None Treasurer and Chief at the discretion Pioneer; Treasurer of all of the Pioneer Funds Financial and of the Board since March 2008; Deputy Treasurer of Amundi Accounting Officer Pioneer from March 2004 to February 2008; and Assistant Treasurer of all of the Pioneer Funds from March 2004 to February 2008 ------------------------------------------------------------------------------------------------------------------------------------ Luis I. Presutti (53) Since 2000. Serves Director - Fund Treasury of Amundi Pioneer; and None Assistant Treasurer at the discretion Assistant Treasurer of all of the Pioneer Funds of the Board ------------------------------------------------------------------------------------------------------------------------------------ Gary Sullivan (60) Since 2002. Serves Senior Manager - Fund Treasury of Amundi Pioneer; None Assistant Treasurer at the discretion and Assistant Treasurer of all of the of the Board Pioneer Funds ------------------------------------------------------------------------------------------------------------------------------------ Pioneer Fund | Annual Report | 12/31/18 53 Fund Officers (continued) ------------------------------------------------------------------------------------------------------------------------------------ Name, Age and Position Term of Office and Other Directorships Held With the Fund Length of Service Principal Occupation Held by Officer ------------------------------------------------------------------------------------------------------------------------------------ David F. Johnson (39) Since 2009. Serves Senior Manager - Fund Treasury of Amundi Pioneer None Assistant Treasurer at the discretion since November 2008; Assistant Treasurer of all of the Board of the Pioneer Funds since January 2009; and Client Service Manager - Institutional Investor Services at State Street Bank from March 2003 to March 2007 ------------------------------------------------------------------------------------------------------------------------------------ John Malone (48) Since 2010. Serves Managing Director, Chief Compliance Officer of None Chief Compliance Officer at the discretion Amundi Pioneer Asset Management; Amundi Pioneer of the Board Institutional Asset Management, Inc.; and the Pioneer Funds since September 2018; and Chief Compliance Officer of Amundi Pioneer Distributor, Inc. since January 2014. ------------------------------------------------------------------------------------------------------------------------------------ Kelly O'Donnell (47) Since 2006. Serves Vice President of Amundi Pioneer Asset Management None Anti-Money at the discretion and Anti-Money Laundering Officer of all the Laundering Officer of the Board Pioneer Funds since 2006 ------------------------------------------------------------------------------------------------------------------------------------ 54 Pioneer Fund | Annual Report | 12/31/18 This page is for your notes. Pioneer Fund | Annual Report | 12/31/18 55 This page is for your notes. 56 Pioneer Fund | Annual Report | 12/31/18 This page is for your notes. Pioneer Fund | Annual Report | 12/31/18 57 This page is for your notes. 58 Pioneer Fund | Annual Report | 12/31/18 This page is for your notes. Pioneer Fund | Annual Report | 12/31/18 59 This page is for your notes. 60 Pioneer Fund | Annual Report | 12/31/18 How to Contact Amundi Pioneer We are pleased to offer a variety of convenient ways for you to contact us for assistance or information. Call us for: -------------------------------------------------------------------------------- Account Information, including existing accounts, new accounts, prospectuses, applications and service forms 1-800-225-6292 FactFoneSM for automated fund yields, prices, account information and transactions 1-800-225-4321 Retirement plans information 1-800-622-0176 Write to us: -------------------------------------------------------------------------------- Amundi Pioneer P.O. Box 219427 Kansas City, MO 64121-9427 Our toll-free fax 1-800-225-4240 Our internet e-mail address us.askamundipioneer@amundipioneer.com (for general questions about Amundi Pioneer only) Visit our web site: www.amundipioneer.com This report must be preceded or accompanied by a prospectus. The Fund files a complete schedule of investments with the Securities and Exchange Commission for the first and third quarters for each fiscal year on Form N-Q. Shareholders may view the filed Form N-Q by visiting the Commission's web site at https://www.sec.gov. [LOGO] Amundi Pioneer ============== ASSET MANAGEMENT Amundi Pioneer Asset Management, Inc. 60 State Street Boston, MA 02109 www.amundipioneer.com Securities offered through Amundi Pioneer Funds Distributor, Inc. 60 State Street, Boston, MA 02109 Underwriter of Pioneer Mutual Funds, Member SIPC [C] 2019 Amundi Pioneer Asset Management 18627-13-0219 ITEM 2. CODE OF ETHICS. (a) Disclose whether, as of the end of the period covered by the report, the registrant has adopted a code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party. If the registrant has not adopted such a code of ethics, explain why it has not done so. The registrant has adopted, as of the end of the period covered by this report, a code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer and controller. (b) For purposes of this Item, the term "code of ethics" means written standards that are reasonably designed to deter wrongdoing and to promote: (1) Honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships; (2) Full, fair, accurate, timely, and understandable disclosure in reports and documents that a registrant files with, or submits to, the Commission and in other public communications made by the registrant; (3) Compliance with applicable governmental laws, rules, and regulations; (4) The prompt internal reporting of violations of the code to an appropriate person or persons identified in the code; and (5) Accountability for adherence to the code. (c) The registrant must briefly describe the nature of any amendment, during the period covered by the report, to a provision of its code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item. The registrant must file a copy of any such amendment as an exhibit pursuant to Item 10(a), unless the registrant has elected to satisfy paragraph (f) of this Item by posting its code of ethics on its website pursuant to paragraph (f)(2) of this Item, or by undertaking to provide its code of ethics to any person without charge, upon request, pursuant to paragraph (f)(3) of this Item. The registrant has made no amendments to the code of ethics during the period covered by this report. (d) If the registrant has, during the period covered by the report, granted a waiver, including an implicit waiver, from a provision of the code of ethics to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, that relates to one or more of the items set forth in paragraph (b) of this Item, the registrant must briefly describe the nature of the waiver, the name of the person to whom the waiver was granted, and the date of the waiver. Not applicable. (e) If the registrant intends to satisfy the disclosure requirement under paragraph (c) or (d) of this Item regarding an amendment to, or a waiver from, a provision of its code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item by posting such information on its Internet website, disclose the registrant's Internet address and such intention. Not applicable. (f) The registrant must: (1) File with the Commission, pursuant to Item 12(a)(1), a copy of its code of ethics that applies to the registrant's principal executive officer,principal financial officer, principal accounting officer or controller, or persons performing similar functions, as an exhibit to its annual report on this Form N-CSR (see attachment); (2) Post the text of such code of ethics on its Internet website and disclose, in its most recent report on this Form N-CSR, its Internet address and the fact that it has posted such code of ethics on its Internet website; or (3) Undertake in its most recent report on this Form N-CSR to provide to any person without charge, upon request, a copy of such code of ethics and explain the manner in which such request may be made. 	See Item 10(2) ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT. (a) (1) Disclose that the registrant's board of trustees has determined that the registrant either: (i) Has at least one audit committee financial expert serving on its audit committee; or (ii) Does not have an audit committee financial expert serving on its audit committee. The registrant's Board of Trustees has determined that the registrant has at least one audit committee financial expert. (2) If the registrant provides the disclosure required by paragraph (a)(1)(i) of this Item, it must disclose the name of the audit committee financial expert and whether that person is "independent." In order to be considered "independent" for purposes of this Item, a member of an audit committee may not, other than in his or her capacity as a member of the audit committee, the board of trustees, or any other board committee: (i) Accept directly or indirectly any consulting, advisory, or other compensatory fee from the issuer; or (ii) Be an "interested person" of the investment company as defined in Section 2(a)(19) of the Act (15 U.S.C. 80a-2(a)(19)). Mr. David R. Bock, an independent trustee, is such an audit committee financial expert. (3) If the registrant provides the disclosure required by paragraph (a)(1) (ii) of this Item, it must explain why it does not have an audit committee financial expert. Not applicable. ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES. (a) Disclose, under the caption AUDIT FEES, the aggregate fees billed for each of the last two fiscal years for professional services rendered by the principal accountant for the audit of the registrant's annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years. The audit fees for the Fund were $ 25,500 payable to Ernst & Young LLP for the year ended December 31, 2018 and $25,500 payable for the year ended December 31, 2017. (b) Disclose, under the caption AUDIT-RELATED FEES, the aggregate fees billed in each of the last two fiscal years for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant's financial statements and are not reported under paragraph (a) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category. There were no audit-related services in 2018 or 2017. (c) Disclose, under the caption TAX FEES, the aggregate fees billed in each of the last two fiscal years for professional services rendered by the principal accountant for tax compliance, tax advice, and tax planning. Registrants shall describe the nature of the services comprising the fees disclosed under this category. The tax fees for the Fund were $8,028 payable to Ernst & Young LLP for the year ended December 31, 2018 and $8,028 for the year ended December 31, 2017 (d) Disclose, under the caption ALL OTHER FEES, the aggregate fees billed in each of the last two fiscal years for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category. There were no other fees in 2018 or 2017. (e) (1) Disclose the audit committee's pre-approval policies and procedures described in paragraph (c)(7) of Rule 2-01 of Regulation S-X. PIONEER FUNDS APPROVAL OF AUDIT, AUDIT-RELATED, TAX AND OTHER SERVICES PROVIDED BY THE INDEPENDENT AUDITOR SECTION I - POLICY PURPOSE AND APPLICABILITY The Pioneer Funds recognize the importance of maintaining the independence of their outside auditors. Maintaining independence is a shared responsibility involving Amudi Pioneer Asset Management, Inc, the audit committee and the independent auditors. The Funds recognize that a Fund's independent auditors: 1) possess knowledge of the Funds, 2) are able to incorporate certain services into the scope of the audit, thereby avoiding redundant work, cost and disruption of Fund personnel and processes, and 3) have expertise that has value to the Funds. As a result, there are situations where it is desirable to use the Fund's independent auditors for services in addition to the annual audit and where the potential for conflicts of interests are minimal. Consequently, this policy, which is intended to comply with Rule 210.2-01(C)(7), sets forth guidelines and procedures to be followed by the Funds when retaining the independent audit firm to perform audit, audit-related tax and other services under those circumstances, while also maintaining independence. Approval of a service in accordance with this policy for a Fund shall also constitute approval for any other Fund whose pre-approval is required pursuant to Rule 210.2-01(c)(7)(ii). In addition to the procedures set forth in this policy, any non-audit services that may be provided consistently with Rule 210.2-01 may be approved by the Audit Committee itself and any pre-approval that may be waived in accordance with Rule 210.2-01(c)(7)(i)(C) is hereby waived. Selection of a Fund's independent auditors and their compensation shall be determined by the Audit Committee and shall not be subject to this policy. SECTION II - POLICY ---------------- -------------------------------- ------------------------------------------------- SERVICE SERVICE CATEGORY DESCRIPTION SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES CATEGORY ---------------- -------------------------------- ------------------------------------------------- I. AUDIT Services that are directly o Accounting research assistance SERVICES related to performing the o SEC consultation, registration independent audit of the Funds statements, and reporting o Tax accrual related matters o Implementation of new accounting standards o Compliance letters (e.g. rating agency letters) o Regulatory reviews and assistance regarding financial matters o Semi-annual reviews (if requested) o Comfort letters for closed end offerings ---------------- -------------------------------- ------------------------------------------------- II. Services which are not o AICPA attest and agreed-upon procedures AUDIT-RELATED prohibited under Rule o Technology control assessments SERVICES 210.2-01(C)(4) (the "Rule") o Financial reporting control assessments and are related extensions of o Enterprise security architecture the audit services support the assessment audit, or use the knowledge/expertise gained from the audit procedures as a foundation to complete the project. In most cases, if the Audit-Related Services are not performed by the Audit firm, the scope of the Audit Services would likely increase. The Services are typically well-defined and governed by accounting professional standards (AICPA, SEC, etc.) ---------------- -------------------------------- ------------------------------------------------- ------------------------------------- ------------------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- ------------------------------------ o "One-time" pre-approval o A summary of all such for the audit period for all services and related fees pre-approved specific service reported at each regularly subcategories. Approval of the scheduled Audit Committee independent auditors as meeting. auditors for a Fund shall constitute pre approval for these services. ------------------------------------- ------------------------------------ o "One-time" pre-approval o A summary of all such for the fund fiscal year within services and related fees a specified dollar limit (including comparison to for all pre-approved specified dollar limits) specific service subcategories reported quarterly. o Specific approval is needed to exceed the pre-approved dollar limit for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for Audit-Related Services not denoted as "pre-approved", or to add a specific service subcategory as "pre-approved" ------------------------------------- ------------------------------------ SECTION III - POLICY DETAIL, CONTINUED ----------------------- --------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- --------------------------- ----------------------------------------------- III. TAX SERVICES Services which are not o Tax planning and support prohibited by the Rule, o Tax controversy assistance if an officer of the Fund o Tax compliance, tax returns, excise determines that using the tax returns and support Fund's auditor to provide o Tax opinions these services creates significant synergy in the form of efficiency, minimized disruption, or the ability to maintain a desired level of confidentiality. ----------------------- --------------------------- ----------------------------------------------- ------------------------------------- ------------------------- AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- ------------------------- ------------------------------------- ------------------------- o "One-time" pre-approval o A summary of for the fund fiscal year all such services and within a specified dollar limit related fees 				 (including comparison 			 to specified dollar 			 limits) reported 			 quarterly. o Specific approval is needed to exceed the pre-approved dollar limits for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for tax services not denoted as pre-approved, or to add a specific service subcategory as "pre-approved" ------------------------------------- ------------------------- SECTION III - POLICY DETAIL, CONTINUED ----------------------- --------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- --------------------------- ----------------------------------------------- IV. OTHER SERVICES Services which are not o Business Risk Management support prohibited by the Rule, o Other control and regulatory A. SYNERGISTIC, if an officer of the Fund compliance projects UNIQUE QUALIFICATIONS determines that using the Fund's auditor to provide these services creates significant synergy in the form of efficiency, minimized disruption, the ability to maintain a desired level of confidentiality, or where the Fund's auditors posses unique or superior qualifications to provide these services, resulting in superior value and results for the Fund. ----------------------- --------------------------- ----------------------------------------------- --------------------------------------- ------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- -------------------------- o "One-time" pre-approval o A summary of for the fund fiscal year within all such services and a specified dollar limit related fees 			 (including comparison 			 to specified dollar 				 limits) reported quarterly. o Specific approval is needed to exceed the pre-approved dollar limits for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for "Synergistic" or "Unique Qualifications" Other Services not denoted as pre-approved to the left, or to add a specific service subcategory as "pre-approved" ------------------------------------- -------------------------- SECTION III - POLICY DETAIL, CONTINUED ----------------------- ------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PROHIBITED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- ------------------------- ----------------------------------------------- PROHIBITED SERVICES Services which result 1. Bookkeeping or other services in the auditors losing related to the accounting records or independence status financial statements of the audit under the Rule. client* 2. Financial information systems design and implementation* 3. Appraisal or valuation services, fairness* opinions, or contribution-in-kind reports 4. Actuarial services (i.e., setting actuarial reserves versus actuarial audit work)* 5. Internal audit outsourcing services* 6. Management functions or human resources 7. Broker or dealer, investment advisor, or investment banking services 8. Legal services and expert services unrelated to the audit 9. Any other service that the Public Company Accounting Oversight Board determines, by regulation, is impermissible ----------------------- ------------------------- ----------------------------------------------- ------------------------------------------- ------------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------------- ------------------------------ o These services are not to be o A summary of all performed with the exception of the(*) services and related services that may be permitted fees reported at each if they would not be subject to audit regularly scheduled procedures at the audit client (as Audit Committee meeting defined in rule 2-01(f)(4)) level will serve as continual the firm providing the service. confirmation that has 				 not provided any restricted services. ------------------------------------------- ------------------------------ -------------------------------------------------------------------------------- GENERAL AUDIT COMMITTEE APPROVAL POLICY: o For all projects, the officers of the Funds and the Fund's auditors will each make an assessment to determine that any proposed projects will not impair independence. o Potential services will be classified into the four non-restricted service categories and the "Approval of Audit, Audit-Related, Tax and Other Services" Policy above will be applied. Any services outside the specific pre-approved service subcategories set forth above must be specifically approved by the Audit Committee. o At least quarterly, the Audit Committee shall review a report summarizing the services by service category, including fees, provided by the Audit firm as set forth in the above policy. -------------------------------------------------------------------------------- (2) Disclose the percentage of services described in each of paragraphs (b) through (d) of this Item that were approved by the audit committee pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X. Non-Audit Services Beginning with non-audit service contracts entered into on or after May 6, 2003, the effective date of the new SEC pre-approval rules, the Fund's audit committee is required to pre-approve services to affiliates defined by SEC rules to the extent that the services are determined to have a direct impact on the operations or financial reporting of the Fund. For the years ended December 31 2018 and 2017, there were no services provided to an affiliate that required the Fund's audit committee pre-approval. (f) If greater than 50 percent, disclose the percentage of hours expended on the principal accountants engagement to audit the registrant's financial statements for the most recent fiscal year that were attributed to work performed by persons other than the principal accountant's full-time, permanent employees. N/A (g) Disclose the aggregate non-audit fees billed by the registrants accountant for services rendered to the registrant, and rendered to the registrants investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant for each of the last two fiscal years of the registrant. The aggregate non-audit fees for the Fund were $8,028 payable to Ernst & Young LLP for the year ended December 31, 2018 and $8,028 for the year ended December 31, 2017. (h) Disclose whether the registrants audit committee of the board of trustees has considered whether the provision of non-audit services that were rendered to the registrants investment adviser (not including any subadviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant's independence. The Fund's audit committee of the Board of Trustees has considered whether the provision of non-audit services that were rendered to the Affiliates (as defined) that were not pre- approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant's independence. ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS (a) If the registrant is a listed issuer as defined in Rule 10A-3 under the Exchange Act (17 CFR 240.10A-3), state whether or not the registrant has a separately-designated standing audit committee established in accordance with Section 3(a)(58)(A) of the Exchange Act (15 U.S.C. 78c(a)(58)(A)). If the registrant has such a committee, however designated, identify each committee member. If the entire board of directors is acting as the registrant's audit committee as specified in Section 3(a)(58)(B) of the Exchange Act (15 U.S.C. 78c(a)(58)(B)), so state. N/A (b) If applicable, provide the disclosure required by Rule 10A-3(d) under the Exchange Act (17 CFR 240.10A-3(d)) regarding an exemption from the listing standards for audit committees. N/A ITEM 6. SCHEDULE OF INVESTMENTS. File Schedule of Investments in securities of unaffiliated issuers as of the close of the reporting period as set forth in 210.1212 of Regulation S-X [17 CFR 210.12-12], unless the schedule is included as part of the report to shareholders filed under Item 1 of this Form. Included in Item 1 ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES. A closed-end management investment company that is filing an annual report on this Form N-CSR must, unless it invests exclusively in non-voting securities, describe the policies and procedures that it uses to determine how to vote proxies relating to portfolio securities, including the procedures that the company uses when a vote presents a conflict between the interests of its shareholders, on the one hand, and those of the company's investment adviser; principal underwriter; or any affiliated person (as defined in Section 2(a)(3) of the Investment Company Act of 1940 (15 U.S.C. 80a-2(a)(3)) and the rules thereunder) of the company, its investment adviser, or its principal underwriter, on the other. Include any policies and procedures of the company's investment adviser, or any other third party, that the company uses, or that are used on the company's behalf, to determine how to vote proxies relating to portfolio securities. Not applicable to open-end management investment companies. ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES. (a) If the registrant is a closed-end management investment company that is filing an annual report on this Form N-CSR,provide the following information: (1) State the name, title, and length of service of the person or persons employed by or associated with the registrant or an investment adviser of the registrant who are primarily responsible for the day-to-day management of the registrant's portfolio ("Portfolio Manager"). Also state each Portfolio Manager's business experience during the past 5 years. Not applicable to open-end management investment companies. ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS. (a) If the registrant is a closed-end management investment company, in the following tabular format, provide the information specified in paragraph (b) of this Item with respect to any purchase made by or on behalf of the registrant or any affiliated purchaser, as defined in Rule 10b-18(a)(3) under the Exchange Act (17 CFR 240.10b-18(a)(3)), of shares or other units of any class of the registrant's equity securities that is registered by the registrant pursuant to Section 12 of the Exchange Act (15 U.S.C. 781). Not applicable to open-end management investment companies. ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS. Describe any material changes to the procedures by which shareholders may recommend nominees to the registrant's board of directors, where those changes were implemented after the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R(17 CFR 229.407)(as required by Item 22(b)(15)) of Schedule 14A (17 CFR 240.14a-101), or this Item. There have been no material changes to the procedures by which the shareholders may recommend nominees to the registrant's board of directors since the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R of Schedule 14(A) in its definitive proxy statement, or this item. ITEM 11. CONTROLS AND PROCEDURES. (a) Disclose the conclusions of the registrant's principal executive and principal financials officers, or persons performing similar functions, regarding the effectiveness of the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR 270.30a-3(c))) as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR 270.30(a)-3(b) and Rules 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)). The registrant's principal executive officer and principal financial officer have concluded that the registrant's disclosure controls and procedures are effective based on the evaluation of these controls and procedures as of a date within 90 days of the filing date of this report. (b) Disclose any change in the registrant's internal control over financial reporting (as defined in Rule 30a-3(d) under the Act (17CFR 270.30a-3(d)) that occured during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting. There were no significant changes in the registrant's internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting. The registrant's principal executive officer and principal financial officer, however, voluntarily are reporting the following information: In August of 2006 the registrant's investment adviser enhanced its internal procedures for reporting performance information required to be included in prospectuses. Those enhancements involved additional internal controls over the appropriateness of performance data generated for this purpose. Such enhancements were made following an internal review which identified prospectuses relating to certain classes of shares of a limited number of registrants where, inadvertently, performance information not reflecting the deduction of applicable sales charges was included. Those prospectuses were revised, and the revised prospectuses were distributed to shareholders. Item 12. Disclosure of Securities Lending Activities for Closed-End Management Investment Companies. (a) If the registrant is a closed-end management investment company, provide the following dollar amounts of income and compensation related to the securities lending activities of the registrant during its most recent fiscal year: N/A (1) Gross income from securities lending activities; N/A (2) All fees and/or compensation for each of the following securities lending activities and related services: any share of revenue generated by the securities lending program paid to the securities lending agent(s) (revenue split); fees paid for cash collateral management services (including fees deducted from a pooled cash collateral reinvestment vehicle) that are not included in the revenue split; administrative fees that are not included in the revenue split; fees for indemnification that are not included in the revenue split; rebates paid to borrowers; and any other fees relating to the securities lending program that are not included in the revenue split, including a description of those other fees; N/A (3) The aggregate fees/compensation disclosed pursuant to paragraph (2); and N/A (4) Net income from securities lending activities (i.e., the dollar amount in paragraph (1) minus the dollar amount in paragraph (3)). If a fee for a service is included in the revenue split, state that the fee is included in the revenue split. N/A (b) If the registrant is a closed-end management investment company, describe the services provided to the registrant by the securities lending agent in the registrants most recent fiscal year. N/A ITEM 13. EXHIBITS. (a) File the exhibits listed below as part of this Form. Letter or number the exhibits in the sequence indicated. (1) Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit. (2) A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2(a)) , exactly as set forth below: Filed herewith. SIGNATURES [See General Instruction F] Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. (Registrant) Pioneer Fund By (Signature and Title)* /s/ Lisa M. Jones Lisa M. Jones, President & Chief Executive Officer Date March 5, 2019 Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated. By (Signature and Title)* /s/ Lisa M. Jones Lisa M. Jones, President & Chief Executive Officer Date March 5, 2019 By (Signature and Title)* /s/ Mark E. Bradley Mark E. Bradley, Treasurer & Chief Accounting & Financial Officer Date March 5, 2019 * Print the name and title of each signing officer under his or her signature.