Use these links to rapidly review the document
TABLE OF CONTENTS

Table of Contents

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A
(Rule 14a-101)

INFORMATION REQUIRED IN
PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

Table of Contents

March 29, 201628, 2017

Dear Fellow Shareholders of ACNB Corporation:

        On behalf of the Board of Directors, I am pleased to invite you to attend our Annual Meeting of Shareholders to be held on Tuesday, May 3, 2016,2, 2017, at 1:00 p.m., prevailing time, at the ACNB Corporation Operations Center, 100 V-Twin Drive, Gettysburg, Pennsylvania 17325. At the annual meeting, you will have the opportunity to ask questions and to make comments. Enclosed with the proxy statement is the notice of meeting, proxy card, ACNB Corporation's 20152016 Annual Review, and ACNB Corporation's 20152016 Annual Report on Form 10-K.

        The principal business of the meeting is to fix the number of Directors of ACNB Corporation at thirteen (13)sixteen (16); to fix the number of Class 1 Directors at five (5)six (6); to fix the number of Class 2 Directors at four (4)six (6); to fix the number of Class 3 Directors at four (4); to elect five (5)four (4) Class 13 Directors to serve for terms of three (3) years and until their successors are elected and qualified; to elect one (1) Class 2 Director to serve for a term of one (1) year and until his successor is elected and qualified; to conduct a non-binding vote on executive compensation; to conduct a non-binding vote on the frequency of non-binding shareholder votes on executive compensation; to ratify the selection of BDO USA, LLP as ACNB Corporation's independent registered public accounting firm; and, to transact any other business that is properly presented at the annual meeting. The notice of meeting and proxy statement accompanying this letter describe the specific business to be acted upon in more detail.

        Whether or not you plan to attend the annual meeting, I urge you to vote as soon as possible by completing, signing and returning the enclosed proxy card in the envelope provided or to vote via the internet or telephone. Your prompt vote will save the Corporation expenses involved in further communications. Your vote is important. Voting by written proxy, internet or telephone will ensure your representation at the annual meeting if you do not attend in person.

        I look forward to seeing you on May 3, 2016,2, 2017, at the Corporation's annual meeting.

Sincerely,

Thomas A. Ritter
President & Chief Executive Officer

Table of Contents

[This page intentionally left blank.]

Table of Contents

ACNB CORPORATION

NASDAQ TRADING SYMBOL: ACNB

acnb.com

NOTICE OF ANNUAL MEETING OF SHAREHOLDERS

AND

PROXY STATEMENT

20162017

Table of Contents

TABLE OF CONTENTS

Proxy Statement

Dated and to be mailed to shareholders on or about March 29, 2016.28, 2017.

Table of Contents

ACNB CORPORATION
16 LINCOLN SQUARE
P.O. BOX 3129
GETTYSBURG, PENNSYLVANIA 17325
(717) 334-3161

NOTICE OF ANNUAL MEETING OF SHAREHOLDERS
TO BE HELD ON MAY 3, 20162, 2017

TO THE SHAREHOLDERS OF ACNB CORPORATION:

        NOTICE IS HEREBY GIVEN that the Annual Meeting of Shareholders of ACNB Corporation will be held at the ACNB Corporation Operations Center, 100 V-Twin Drive, Gettysburg, Pennsylvania 17325 on Tuesday, May 3, 2016,2, 2017, at 1:00 p.m., prevailing time, for the purpose of considering and voting upon the following matters:

1.

To fix the number of Directors of ACNB Corporation at thirteen (13)sixteen (16);



2.

To fix the number of Class 1 Directors at five (5)six (6);



3.

To fix the number of Class 2 Directors at four (4)six (6);



4.

To fix the number of Class 3 Directors at four (4);



5.

To elect five (5)four (4) Class 13 Directors to serve for terms of three (3) years and until their successors are elected and qualified;



6.

To elect one (1) Class 2 Director to serve for a term of one (1) year and until his successor is elected and qualified;



7.

To conduct a non-binding vote on executive compensation;



7.8.

To conduct a non-binding vote on the frequency of non-binding shareholder votes on executive compensation;



9.

To ratify the selection of BDO USA, LLP as ACNB Corporation's independent registered public accounting firm; and,



8.10.

To transact such other business as may properly come before the 20162017 Annual Meeting and any adjournment or postponement thereof.

        Only those shareholders of record, at the close of business on March 14, 2016,13, 2017, are entitled to notice of and to vote at the meeting.

        Please promptly sign the enclosed proxy card and return it in the enclosed postage-paid envelope or vote by internet or telephone. We cordially invite you to attend the meeting. Your proxy is revocable and you may withdraw it at any time prior to it being voted. You may deliver notice of revocation or deliver a later dated proxy to the Secretary of the Corporation before the vote at the meeting.

        The Corporation's Board of Directors is distributing the proxy statement, proxy card, ACNB Corporation's 20152016 Annual Review, and ACNB Corporation's 20152016 Annual Report on Form 10-K on or about March 29, 2016.28, 2017.

		BY ORDER OF THE BOARD OF DIRECTORS,
		Thomas A. Ritter President & Chief Executive Officer

Gettysburg, Pennsylvania
March 29, 201628, 2017

YOUR VOTE IS IMPORTANT.
PLEASE COMPLETE, SIGN, DATE AND RETURNVOTE YOUR PROXY CARD.TODAY.

Table of Contents

[This page intentionally left blank.]

Table of Contents

PROXY STATEMENT

GENERAL INFORMATION

Date, Time and Place of the Annual Meeting

        ACNB Corporation, a Pennsylvania business corporation and registered financial holding company, furnishes this proxy statement in connection with the solicitation by the Board of Directors of proxies to be voted at the Corporation's Annual Meeting of Shareholders. The Annual Meeting of Shareholders will be held on Tuesday, May 3, 2016,2, 2017, at 1:00 p.m., prevailing time, at the ACNB Corporation Operations Center, 100 V-Twin Drive, Gettysburg, Pennsylvania 17325. Included with this proxy statement is a copy of ACNB Corporation's 20152016 Annual Review and ACNB Corporation's 20152016 Annual Report on Form 10-K for the fiscal year ended December 31, 2015.2016.

        The Corporation's principal executive office is located at 16 Lincoln Square, Gettysburg, Pennsylvania 17325. The Corporation's telephone number is (717) 334-3161. All inquiries regarding the annual meeting should be directed to Lynda L. Glass, Executive Vice President, President/Secretary & Chief Governance Officer of ACNB Corporation, at (717) 339-5085.

Description of ACNB Corporation

        ACNB Corporation was formed in 1982 and became the holding company for the banking subsidiary in 1983. ACNB Corporation's wholly-owned banking subsidiary is ACNB Bank, a Pennsylvania state-chartered bank and trust company, formerly Adams County National Bank. The Corporation's primary activity consists of owning and supervising its banking subsidiary.

        The Corporation also owns and supervises Russell Insurance Group, Inc. as its insurance subsidiary.

        We have not authorized anyone to provide you with information about the Corporation; therefore, you should rely only on the information contained in this document or on documents to which we refer you. Although we believe we have provided you with all the information helpful to you in your decision to vote, events may occur at ACNB Corporation subsequent to printing this proxy statement that might affect your decision or the value of your stock.

Internet Availability of Proxy Materials

        Important Notice Regarding the Availability of Proxy Materials for the Shareholder Meeting to Be Held on May 3, 2016.2, 2017. The notice of meeting, proxy statement, proxy card, ACNB Corporation's 20152016 Annual Review, and ACNB Corporation's 20152016 Annual Report on Form 10-K are available atacnb.com under the Investor Relations/ACNB Corporation tab or directly athttps://www.acnb.com/acnb-corporation.

VOTING PROCEDURES

Solicitation and Voting of Proxies

        The Board of Directors solicits this proxy for use at the Corporation's 20162017 Annual Meeting of Shareholders. The Corporation's directors and officers and ACNB Bank employees may solicit proxies in person or by telephone, facsimile, email or other similar electronic means without additional compensation. The Corporation will pay the cost of preparing, assembling, printing, mailing and soliciting proxies and any additional material that the Corporation sends to its shareholders. The Corporation will make arrangements with brokerage firms and other custodians, nominees and fiduciaries to forward proxy solicitation materials to the beneficial owners of stock held by these entities, as well as will reimburse these third parties for their reasonable forwarding expenses. This proxy statement and the related proxy card are being distributed on or about March 29, 2016.28, 2017.

Table of Contents

        Shareholders of record at the close of business on March 14, 201613, 2017 (the annual meeting record date), are entitled to vote at the meeting. The Corporation's records show that, as of the annual meeting record date, 6,039,7246,064,138 shares of the Corporation's common stock, par value $2.50 per share, were outstanding. On all matters to come before the annual meeting, shareholders may cast one (1) vote for each share held. Cumulative voting rights do not exist with respect to the election of directors.

        You may vote your shares by completing and returning a written proxy card or voting by internet or telephone. You may also vote in person at the meeting. Submitting your voting instructions by returning a proxy card, internet or telephone will not affect your right to attend the meeting and vote, if you later decide to attend in person. If your shares are registered directly in your name with ACNB Corporation's transfer agent, Computershare, you are considered, with respect to those shares, the shareholder of record, and these proxy materials are being sent directly to you by the Corporation. As the shareholder of record, you have the right to grant your voting proxy directly to the proxyholders or to vote in person at the meeting. The Corporation has enclosed a proxy card, as well as instructions to vote by internet or telephone, for your use.

        If your shares are held in a stock brokerage account or by a bank or other nominee, you are considered the beneficial owner of shares held in street name, and these proxy materials are being forwarded to you by your broker or nominee which is considered, with respect to those shares, the shareholder of record. As the beneficial owner, you have the right to direct your broker or nominee how to vote and you are also invited to attend the meeting. However, because you are not the shareholder of record, you may not vote your street name shares in person at the meeting, unless you obtain a proxy executed in your favor from the holder of record. Your broker or nominee has enclosed a voting instruction card for you to use in directing the broker or nominee how to vote your shares.

        By properly completing a proxy, you appoint Scott L. KelleyJames J. Lott and Alan J. StockMarian B. Schultz as proxyholders to vote your shares, as indicated on the proxy card. Any signed proxy card or vote by internet or telephone not specifying to the contrary will be votedFOR:

1.

Fixing the number of Directors of ACNB Corporation at thirteen (13)sixteen (16);



2.

Fixing the number of Class 1 Directors at five (5)six (6);



3.

Fixing the number of Class 2 Directors at four (4)six (6);



4.

Fixing the number of Class 3 Directors at four (4);



5.

Electing five (5)four (4) Class 13 Directors to serve for terms of three (3) years and until their successors are elected and qualified;



6.

Electing one (1) Class 2 Director to serve for a term of one (1) year and until his successor is elected and qualified;



7.

Approving the non-binding vote on executive compensation;



8.

Approving the non-binding vote on the frequency of non-binding shareholder votes on executive compensation for one (1) year; and,



7.9.

Ratifying the selection of BDO USA, LLP as ACNB Corporation's independent registered public accounting firm.

        You may revoke your written proxy by delivering written notice of revocation to Lynda L. Glass, Executive Vice President, President/Secretary & Chief Governance Officer of the Corporation, by executing a later dated proxy and giving written notice of the revocation to Ms. Glass or voting again by internet or telephone at any time before the proxy is voted at the meeting. Proxyholders will vote shares

Table of Contents

represented by proxies on the accompanying proxy card, if properly signed and returned, or by internet or telephone in accordance with instructions from shareholders.

        Although the Board of Directors knows of no other business to be presented, in the event that any other matters are properly brought before the meeting, any proxy given pursuant to this solicitation will be voted in accordance with the recommendations of the Board of Directors. This proxy statement is being mailed to the Corporation's shareholders on or about March 29, 2016.

Table of Contents

Quorum and Vote Required for Approval

        As of the close of business on March 14, 2016,13, 2017, the Corporation had 6,039,7246,064,138 shares of common stock, par value $2.50 per share, outstanding.

        Under Pennsylvania law and ACNB Corporation's Bylaws, the presence of a quorum is required for each matter to be acted upon at the meeting. A majority of the outstanding shares of common stock, represented in person or by proxy, constitutes a quorum. Votes withheld and abstentions are counted in determining the presence of a quorum for a particular matter. Broker non-votes are not counted in determining the presence of a quorum for a particular matter as to which the broker withheld authority. Each share is entitled to one (1) vote on all matters submitted to a vote of the shareholders. All matters to be voted upon by the shareholders require the affirmative vote of a majority of shares voted, in person or by proxy, at the annual meeting, except in cases where the vote of a greater number of shares is required by law or under ACNB Corporation's Articles of Incorporation or Bylaws. In the case of the election of directors, the candidates receiving the highest number of votes are elected. Shareholders are not entitled to cumulate votes for the election of directors.

        If a quorum is present, fixing the number of directors of the Board of Directors, fixing the number of directors in each class, approving the non-binding proposal on executive compensation, and ratifying the independent registered public accounting firm for the year ending December 31, 2016,2017, requires the affirmative"FOR" vote of a majority of all votes cast, in person or by proxy. Abstentions and broker non-votes are not deemed to constitute "votes cast" and, therefore, do not count either for or against the proposals. Abstentions and broker non-votes, however, have the practical effect of reducing the number of affirmative votes required to achieve a majority for the matter by reducing the total number of shares voted from which the required majority is calculated.

        If a quorum is present, the shareholders will elect the nominees for director receiving the highest number of"FOR" votes cast by those shareholders entitled to vote for the election of directors. Shareholders will approve the frequency of the non-binding vote on executive compensation by a plurality of votes cast on the matter. The proxyholders will not cast votes for or against any director nominees or for any specific year frequency when the broker withheld authority.

GOVERNANCE OF THE CORPORATION

        Our Board of Directors believes that the purpose of corporate governance is to ensure that we maximize shareholder value in a manner consistent with legal requirements and the highest standards of integrity. The Board has adopted and adheres to corporate governance practices which the Board and executive management believe promote this purpose, are sound, and represent best practices. We continually review these governance practices, Pennsylvania law (the state in which we are incorporated), rules and listing standards of The Nasdaq Stock Market, SEC regulations, as well as best practices suggested by recognized governance authorities. Currently, our Board of Directors has thirteen (13) members. Under the SEC and Nasdaq standards for independence, all non-employee directors and nominees meet the standards for independence. This constitutes more than a majority of our Board of Directors. Only independent directors serve on our Audit Committee, Nominating Committee, and Compensation Committee.

Table of Contents

Leadership Structure

        The Corporation chooses to separate the roles of Chairman and President & Chief Executive Officer. The President & Chief Executive Officer is responsible for implementing the strategic direction of the Corporation, as determined by the Board of Directors, and for the day-to-day leadership and performance of the Corporation. The Chairman oversees the agenda for and presides over Board of Director meetings, as well as provides leadership to the Board and facilitates communication between

Table of Contents

the Board of Directors and executive management. The Corporation's Chairman of the Board is considered independent under the SEC and Nasdaq standards for independence.

Risk Oversight

        The Board of Directors has a role in overseeing the Corporation's risks as a whole and at the committee level. The Audit Committee is primarily responsible for overseeing the risks the Corporation faces on behalf of the Board of Directors. The Audit Committee works closely with the Corporation's Chairman of the Board, President & Chief Executive Officer, and ACNB Bank's Chief Risk & Governance Officer, as well as with other members of management with respect to matters relating to risk management. The Audit Committee receives reports on risk management and the processes in place to monitor and control such exposures. The Audit Committee may also receive updates, from time to time, between meetings from management relating to risk oversight matters. The Audit Committee provides updates on its risk management activities to the full Board of Directors via the committee's meeting minutes. Further, members of management may make presentations on risk management to the full Board of Directors or another committee of the Board of Directors.

        In addition to the Audit Committee, other committees of the Board of Directors consider the risks within their areas of responsibility. For example, the Compensation Committee considers the risks that may be implicated by the Corporation's compensation practices. Also, the Strategic Planning Committee assesses the risks associated with the Corporation's executive management succession plans.

Director Independence

        In determining each director's and nominee's independence, the Board of Directors considered loan transactions between ACNB Bank and the individuals, their family members, and businesses with which they are associated. The table below includes a description of other categories or types of transactions, relationships or arrangements considered by the Board (in addition to those listed above and those transactions set forth under "Transactions with Directors and Executive Officers" below) in reaching its determination that the directors are independent.

        In each case, the Board of Directors determined that none of the transactions impaired the independence of the director.

Table of Contents

Directors of ACNB Corporation

        The following table sets forth, as of March 14, 201613, 2017 (in alphabetical order), selected information about the Corporation's directors and director nominees.

Table of Contents

Executive Officers of ACNB Corporation and/or Subsidiary

        The following table sets forth, as of March 14, 2016,13, 2017, selected information about the Corporation's Executive Officers, each of whom is appointed by the Board of Directors and each of whom holds office at the Board's discretion.

Table of Contents

Meetings and Committees of the Board of Directors

        The Board of Directors of ACNB Corporation met twelve (12)fifteen (15) times during 2015.2016. The Corporation maintains an Audit Committee (which is established in accordance with Section 3(a)(58)(A) of the Securities Exchange Act of 1934), Executive Committee, Compensation Committee, Nominating Committee, and Strategic Planning Committee. A total of thirty-four (34)thirty-seven (37) Board and committee meetings of the Corporation's Board of Directors were held in 2015.2016. During 2015,2016, each of the directors attended at least 75% of the combined total number of meetings of the Corporation's Board of Directors and the committees of which he or she was a member, except Richard L. Alloway II and Harry L. Wheeler who retired as of May 5, 2015.member. The Board of Directors has a written attendance policy statement which encourages and expects each director to attend the Annual Meeting of Shareholders. All of theTwelve (12) directors and one (1) director nominee attended the 20152016 Annual Meeting of Shareholders, and we expect that they will all attend the 20162017 Annual Meeting of Shareholders.

        Audit Committee.    Members of the Audit Committee during 20152016 were Daniel W. Potts, who served as Chair, Richard L. Alloway II, Frank Elsner, III, Robert W. Miller, Donna M. Newell, J. Emmett Patterson, Marian B. Schultz and David L. Sites and Harry L. Wheeler.Sites. Each of these directors is "independent" as defined in the SEC and Nasdaq standards for independence. In addition, Thomas A. Ritter, David W. Cathell, Lynda L. Glass and James P. Helt were invited to attend committee meetings. The principal duties of the Audit Committee, as set forth in its charter, include reviewing the Corporation's financial reporting process and systems of internal accounting and financial controls; reviewing significant audit

Table of Contents

and accounting principles, policies and practices; reviewing performance of internal auditing procedures; overseeing risk management; and, recommending annually to the Board of Directors the engagement of an independent auditor. The Audit Committee has a charter which is available under the Corporate Governance Documents section of the Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com. The Audit Committee met five (5) times during 2015.2016.

        Executive Committee.    Members of the Executive Committee during 20152016 were Frank Elsner, III, who served as Chair, Daniel W. Potts, Marian B. Schultz, David L. Sites, Alan J. Stock and James E. Williams. Each of these directors is "independent" as defined in the SEC and Nasdaq standards for independence. In addition, Thomas A. Ritter and James P. Helt served as an ex-officio membermembers of this committee, and David W. Cathell and Lynda L. Glass and James P. Helt were invited to attend committee meetings. The principal duties of the Executive Committee are to act on behalf of the Board between meetings and to evaluate governance issues. The Executive Committee has a charter which is available under the Corporate Governance Documents section of the Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com. The Executive Committee met one (1) time during 2015.2016.

        Compensation Committee.    Members of the Compensation Committee during 20152016 were James E. Williams, who served as Chair, Frank Elsner, III, Scott L. Kelley, James J. Lott, J. Emmett Patterson, Marian B. Schultz and Alan J. Stock. Each of these directors is "independent" as defined in the SEC and Nasdaq standards for independence. The principal duties of the Compensation Committee include evaluating and recommending to the Board of Directors the executive officer compensation plans, policies and programs of the Corporation. The Compensation Committee has a charter which is available under the Corporate Governance Documents section of the Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com. The Compensation Committee met seven (7)ten (10) times during 2015.2016.

        Nominating Committee.    Members of the Nominating Committee during 20152016 were Marian B. Schultz, who served as Chair, Richard L. Alloway II, Frank Elsner, III, Donna M. Newell, Alan J. Stock Harry L. Wheeler and James E. Williams. Each of these directors is "independent" as defined in the SEC and Nasdaq standards for independence. The principal duties of the Nominating Committee include identifying qualified individuals to serve on the Board and recommending nominees to the Board. The Nominating Committee has a charter which is available under the Corporate Governance Documents section of the

Table of Contents

Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com. The Nominating Committee met one (1) time during 2015.2016.

        Strategic Planning Committee.    Members of the Strategic Planning Committee during 20152016 were Frank Elsner, III, who served as Chair, Daniel W. Potts, Thomas A. Ritter, Marian B. Schultz, David L. Sites, Alan J. Stock and James E. Williams. The principal duties of the Strategic Planning Committee include overseeing the development of and monitoring the progress of the Corporation's strategic plan; keeping the Board of Directors informed of developments, trends and opportunities in the industry that might help improve the Corporation's profitability, growth and/or customer service; and, establishing Board and senior management succession plans. The Strategic Planning Committee has a charter which is available under the Corporate Governance Documents section of the Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com. The Strategic Planning Committee met eight (8)five (5) times during 2015.2016.

Shareholder Communications

        The Board of Directors has formal shareholder communications processes for the submission of shareholder proposals and nomination of directors, as described below. In addition, shareholders may contact any member of the Board personally, by telephone or by written correspondence including email. Written communications received by the Corporation from shareholders are shared with the full Board as deemed appropriate.

Table of Contents

Submission of Shareholder Proposals

        In order for a shareholder proposal (other than director nominations) to be considered for inclusion in ACNB Corporation's proxy statement for next year's annual meeting, the written proposal must be received by the Corporation no later than November 29, 2016.28, 2017. Proposals may be sent to Lynda L. Glass, Executive Vice President, President/Secretary & Chief Governance Officer of ACNB Corporation, at 16 Lincoln Square, P.O. Box 3129, Gettysburg, Pennsylvania 17325.

        All proposals must comply with SEC regulations regarding the inclusion of shareholder proposals in company-sponsored proxy materials. If a shareholder proposal is submitted to the Corporation after November 29, 2016,28, 2017, it is considered untimely; and, although the proposal may be considered at the annual meeting, the Corporation is not obligated to include it in the 20172018 proxy statement.

Employee Code of Ethics

        Since May 1994, ACNB Bank, formerly Adams County National Bank, has had a Conflict of Interest/Code of Ethics. In 2003, as required by law and regulation, the Corporation's Board of Directors adopted a Code of Ethics which is applicable to our directors, officers and employees, and which has been amended as necessary from time to time.

        The Code of Ethics encourages individuals to report any conduct that they believe in good faith to be an actual or apparent violation of the Code of Ethics to ACNB Corporation's Chief Governance Officer. The Code of Ethics is available under the Corporate Governance Documents section of the Investor Relations/ACNB Corporation page of ACNB Bank's website at www.acnb.com.

Table of Contents

ELECTION OF DIRECTORS

Nomination of Directors

        The Corporation has a standing Nominating Committee with a charter. Recommendations to the Board of Directors as to the nominees for election as directors at the Annual Meeting of Shareholders are provided by the Nominating Committee. The Nominating Committee will consider shareholder-recommended nominees for director, and shareholders who desire to propose an individual for consideration by the Board of Directors as a nominee for director should submit a recommendation in writing to the Secretary of the Corporation in compliance with the requirements of Article II, Sections 202, 203 and 205(b), of the Corporation's Bylaws. Any shareholder who intends to nominate a candidate for election to the Board of Directors must notify the Secretary of the Corporation in writing not less than fourteen (14) days prior to the date of any shareholder meeting called for the election of directors.

Qualification and Nomination of Directors

        The Corporation's Articles of Incorporation authorize the number of directors to be not less than five (5) and not more than twenty-five (25). Further, the Corporation's Articles of Incorporation and Bylaws provide for three (3) classes of directors with staggered terms of office of three (3) years that expire at successive annual meetings. Pursuant to Article II, Section 205, of the Corporation's Bylaws, no director or nominee shall stand for election, if as of the date of election, he or she shall have attained the age of seventy-two (72) years old. Currently, the number of directors is set at thirteen (13): Class 1 consists of five (5) directors, Class 2 consists of four (4) directors, and Class 3 consists of four (4) directors. However, pursuant to Article 11 of the Corporation's Articles of Incorporation and Article I, Section 105, of the Corporation's Bylaws, at each shareholder meeting for the election of directors, the shareholders determine how many directors will be elected to serve in each class. The Board of Directors believes that it is in the Corporation's best interest to fix the number of directors at the 20162017 Annual Meeting at thirteen (13)sixteen (16).

Table of Contents

        The proposed thirteen (13)sixteen (16) member Board of Directors will consist of five (5)six (6) Class 1 Directors, four (4)six (6) Class 2 Directors, and four (4) Class 3 Directors. Two (2) Class 1 Director seats shall be vacant and one (1) Class 2 Director seat shall be vacant. Due to Mr. Miller's resignation from the board, the Board of Directors believes it is in the best interests of the Corporation to leave his Class 1 Director seat vacant should a suitable candidate be identified to fill the seat. Currently, the Board of Directors has not identified any such candidate. In addition, in connection with the proposed acquisition of New Windsor Bancorp, Inc., the Corporation has agreed to increase the total number of directors that constitute the whole board to sixteen (16) and two (2) seats shall be reserved for New Windsor Bancorp, Inc.'s director nominees who meet the Corporation's requirements for board service. Should the proposed transaction be consummated, the Board of Directors currently expects to appoint Todd L. Herring as a Class 1 Director and D. Arthur Seibel, Jr. as a Class 2 Director. Each are currently directors of New Windsor Bancorp, Inc.

Shareholders will elect five (5)four (4) Class 13 Directors to serve for terms of three (3) years until their successors are elected and qualified and one (1) Class 2 Director to serve for a term of one (1) year until his successor is elected and qualified.

        The Nominating Committee believes that a director nominee must have the following attributes/qualifications before being recommended as a nominee: stock ownership in the Corporation, the willingness to commit time, a commitment to independence, a commitment to the Corporation's community, financial competence, a good reputation, integrity, good communication skills, and the willingness and ability to speak up for the interests of the Corporation. A director nominee shall also have expertise that strengthens the Board of Directors. When evaluating potential director nominees, the Nominating Committee considers the skills and expertise of the current Board members and seeks director nominees with knowledge, skills and abilities that enhance and complement—rather than duplicate—the experiences and skills already represented on the Board of Directors. Further, the Nominating Committee ensures director nominees complement the Corporation's strategic vision and direction, a fundamental priority for the Board of Directors. The Nominating Committee follows the same process for evaluating shareholder-recommended nominees for director.

        The Nominating Committee does not have a formal policy with respect to diversity; however, the Board and the Nominating Committee believe that it is essential that members of the Board of Directors represent diverse viewpoints and experience. In considering candidates for the Board, the Nominating Committee considers the entirety of each candidate's credentials in the context of these standards.

Table of Contents

        The Board of Directors nominated incumbent directors James J. Lott, RobertFrank Elsner, III, Scott L. Kelley and Daniel W. Miller, J. Emmett Patterson, Marian B. Schultz and James E. WilliamsPotts to serve as Class 13 Directors until the expiration of the term of the class or until their earlier death, resignation or removal from office. Ms. SchultzFurthermore, after the Nominating Committee considered various internal and external factors, including the fact that he will become President & Chief Executive Officer of the Corporation and ACNB Bank on May 5, 2017, upon the recommendation and approval of the Nominating Committee, the Board of Directors nominated James P. Helt to serve as a Class 3 Director until the expiration of the term of the class or until his earlier death, resignation or removal from office. The Board of Directors nominated incumbent director, Thomas A. Ritter, to serve as a Class 2 Director until the expiration of the term of the class or until his earlier death, resignation or removal from office. Messrs. Lott, Miller, PattersonElsner, Kelley, Potts and WilliamsRitter are presently members of the Board of Directors and have consented to serve another term as a director if reelected. Mr. Helt is a new nominee to the Board of Directors and has consented to serve if elected. If any of the nominees should be unavailable to serve for any reason, a majority of the Board of Directors then in office may fill the vacancy until the expiration of the term of the class of directors to which he or she was appointed.

Table of Contents

        The proxyholders intend to vote all proxies for the election of each of the nominees named below, unless you indicate that your vote should be withheld from any or all of them.

        The Board of Directors proposes the following nominees for election as Class 13 Directors at the annual meeting:

Class 13 Director Nominees

        The Board of Directors proposes the following nominee for election as a Class 2 Director at the annual meeting:

Class 2 Director Nominee

Thomas A. Ritter

        The Board of Directors recommends that shareholders voteFOR the proposalproposals to elect the nominees listed above.

Information as to Nominees and Directors

        Set forth below, as of March 14, 2016,13, 2017, are the principal occupations and certain other information regarding nominees for director and continuing directors including the experience, qualifications, attributes or skills that contribute to the nominee's or director's ability to oversee the management of the Corporation. Unless otherwise specified, all business experience is for the past five (5) years in the same or similar position. You will find information about their share ownership on pages 1214 through 14.16.

Class 1 Directors (to serve until 2016; nominees to serve until 2019 if duly elected and qualified)2019)

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

SHARE OWNERSHIP

Principal Shareholders

        As of December 31, 2015,2016, the Board of Directors knows of no person who owns of record or who is known to be the beneficial owner of more than 5% of the Corporation's outstanding common stock.

Beneficial Ownership of Executive Officers, Directors and Nominees

        The following table sets forth, as of December 31, 2015,2016, and from information received from the respective individuals, the amount and percentage of the common stock beneficially owned by each director, each nominee for director, each Named Executive Officer, and all Named Executive Officers, directors and nominees of the Corporation as a group. Unless otherwise noted, shares are held individually and the percentage of class is less than 1% of the outstanding common stock.

        Beneficial ownership of shares of ACNB Corporation common stock is determined in accordance with SEC Rule 13d-3, which provides that a person should be credited with the ownership of any stock held, directly or indirectly, through any contract, arrangement, understanding, relationship, or otherwise has or shares:

•

Voting power, which includes the power to vote or to direct the voting of the stock; or,



•

Investment power, which includes the power to dispose or direct the disposition of the stock; or,



•

The right to acquire beneficial ownership within sixty (60) days after December 31, 2015.2016.

Table of Contents

        Unless otherwise indicated in a footnote appearing below the table, all shares reported in the table below are owned directly and individually by the reporting person. The number of shares owned by the directors, nominees and executive officersNamed Executive Officers is rounded to the whole share.

Table of Contents

Table of Contents

COMPENSATION AND PLAN INFORMATION

Compensation of the Board of Directors of ACNB Corporation and Subsidiaries

        Directors of the Corporation are not compensated for their services. Further, ACNB Bank does not compensate employee directors for attendance at Board of Directors meetings or committee meetings. However, beginningBeginning April 1, 2015,2016, ACNB Bank's non-employee directors werehave been compensated for their services rendered to the Corporation and to ACNB Bank as follows:

•

$12,00017,000 annual retainer;



•

$550650 per Board meeting;



•

$225 per hour for committee meetings with a minimum payment of $225;



•

$200 for committee chair per meeting, unless otherwise specified;



•

$300400 for Audit Committee chair per meeting;



•

$300400 for Compensation Committee chair per meeting;



•

$2,0002,250 per month for Chairman of the Board;



•

$600 allowance for a half-day seminar plus expenses, if applicable, and $1,000 allowance for a full-day seminar plus expenses, if applicable; and,



•

$125 per hour for continuing education by external, online web-based training, given preapproval.

        Fifty percent (50%) of each director's annual retainer, as paid on a quarterly basis, is submitted as a voluntary cash purchase of ACNB Corporation common stock through the Corporation's Dividend Reinvestment and Stock Purchase Plan.

The following table summarizes the compensation of directors during 2015:2016:

Table of Contents

⁽⁵⁾

Director Deferred Fee Plan

        In January 2001, ACNB Bank established a director deferred fee plan. Directors Alloway, Elsner, Kelley, Lott, Miller, Newell, Patterson, Schultz, Sites, Stock Wheeler and Williams participated in 2015.2016. Directors may defer up to 100% of the director's income. Benefits are payable upon termination of service, change of control, and by specific participant election in accordance with IRS Code Section 409A. The deferred fees earn interest, and the interest and plan expenses are funded by bank-owned life insurance (BOLI).

Director Supplemental Life Insurance Plan

        ACNB Bank has a director supplemental life insurance plan. All non-employee directors are eligible for the life insurance benefit. The plan currently insures twelve (12) directors. The director life insurance benefit of $250,000 per participating director shall be provided unless the director separates from service prior to reaching the retirement age, in which case the benefit is $100,000. This life insurance benefit is funded through a single premium BOLI program because BOLI is a more cost-efficient way of providing the benefits. The amounts of death benefits is the amount set forth in the individual's policy endorsement. The eligible participating directors are not required to pay any premiums on the life insurance policy, but have the imputed value of the insurance coverage included in their taxable incomes.

Long-Term Care Insurance

        ACNB Bank provides long-term care insurance to directors, and eligibility is subject to medical underwriting acceptance. The plan currently insures nine (9) directors. The eligible participating directors are not required to pay any premiums. The long-term care insurance provides a monthly maximum base benefit of $4,000 for long-term care needs.

Table of Contents

Executive Compensation

Compensation Discussion and Analysis

Named Executive Officers

        The Compensation Committee is charged with recommending to the Board of Directors of ACNB Corporation the compensation for all of the Named Executive Officers. For the year 2015,2016, our Named Executive Officers include those individuals in the following table:

Corporation Performance vs. Named Executive Officer Base Salary Increase

        The Corporation is committed to maintaining a strong, healthy financial institution and is committed to our shareholders. We highlight below our corporate performance and the Named

Table of Contents

Executive Officers' (except the President & Chief Executive Officer of Russell Insurance Group, Inc.) base salary which is the main component of our Named Executive Officers' compensation.

Compensation Objectives and Policies

        The primary objectivesobjective of the Corporation's compensation philosophy remainremains to attract, motivate, reward and retain executives who

•

will maintain the safety and soundness of the Corporation and its subsidiaries,



•

subsidiaries. In addition, the Corporation's compensation philosophy aims to sustain and enhance long-term investor value,



•

enforce internal controls deemed appropriate by our auditors and regulators, and



•

execute the strategic plans as prioritized by the Board of Directors.

        The Compensation Committee and the Board of Directors of the Corporation seek to establish fair compensation policies in order to attract, motivate, reward and retain competent managers whose efforts will enhance the Corporation's profitability and growth without exposing the Corporation to undue risk. The Compensation Committee treats compensation as an evolving process depending on the strategic objectives of the Corporation, as determined by the Board of Directors at that time.

The Role of the Executive Officers in Setting Compensation

        The Named Executive Officers do not participate in the determination process of their respective annual base salaries and are not present when their respective compensation is discussed by the Compensation Committee or discussed and approved by the Board of Directors.

        In 2015,2016, the President & Chief Executive Officer of the Corporation provided insight to the Compensation Committee on the performance and compensation of the other Named Executive Officers as illustrated below. The President & Chief Executive Officer of the Corporation also assisted in establishing performance goals and objectives for the other Named Executive Officers, with the exception of Mr. Russell. In addition, the President of ACNB Bank provided the Compensation Committee with his insight on future compensation and equity awards.

Table of Contents

The Compensation Process for the Named Executive Officers,
except the President & Chief Executive Officer of Russell Insurance Group, Inc.

Table of Contents

The Compensation Process for the President & Chief Executive Officer
of Russell Insurance Group, Inc.

Table of Contents

The Role of a Consultant in Setting Compensation

        The Compensation Committee may in its sole discretion retain or seek the advice of a compensation consultant or other adviser. The Compensation Committee is directly responsible for retaining, determining the independence, determining if a conflict of interest exists, compensating, and overseeing the work of its advisers.

        The Compensation Committee chose not to engageengaged Mosteller & Associates ("Mosteller"), a particular compensation consultant for the year 2015.consulting firm in 2016. The Compensation Committee did, however, reviewdetermined that Mosteller was independent and considerthat no conflict of interest existed. Mosteller was charged with updating the peer group to be used by the Compensation Committee and providing peer executive compensation information which the Compensation Committee considered when making recommendations related to executive compensation and bonus awards. The Compensation Committee also reviewed and considered educational materials from various seminars and conferences, as well as other resources, as further explained inBenchmarking below.

Benchmarking

        In 2016, the Compensation Committee engaged Mosteller to present compensation comparisons for peer institutions. Mosteller provided a two-part executive compensation study report. In creating the first comparison, Mosteller used compensation data from five surveys: (1) ERI which included commercial banks with approximately $1.2 billion in assets in the mid-Atlantic region focusing on the Gettysburg/York PA metropolitan area; (2) CompAnalyst which included the financial services industry with approximately $1 to $2 billion in assets focusing on the Gettysburg/York PA metropolitan area; (3) Towers Watson which focused on the financial services industry with less than $5 billion in assets nationwide; (4) L.R. Webber Associates, Inc.'s 2015 Salary & Benefits Survey which focused on financial institutions with greater than $1 billion in assets; and, (5) Mosteller & Associates' proprietary database of regional banks with assets from $1 to $2 billion primarily in the mid-Atlantic region. The compensation data below compares the salary and bonus compensation level by position to the average compensation levels reflected in the market surveys. Mr. Russell's compensation was not analyzed in this comparison based upon the contractual nature of his compensation.

        As illustrated below, the base compensation for the Named Executive Officers fell between the 50^th and 75^th percentiles, except for the compensation of Mr. Ritter which fell between the 25^th and 50^th percentiles. The total cash component of the Named Executive Officers fell between the 25^th and 50^th percentiles, except for the total cash paid to Mr. Ritter which fell below the 25^th percentile.