IMPORTANT INFORMATION

We intend to hold the Annual Meeting in person. However, we are sensitive to the public health and travel concerns our stockholders may have and recommendations that public health officials may issue in light of the evolving coronavirus (COVID-19) situation. As a result, we may impose additional procedures or limitations on Annual Meeting attendees, or we may decide to hold the Annual Meeting at a different location or by means of remote communication. We plan to announce any such updates on our proxy website (https://investor.mantech.com/shareholder-resources/annual-meeting), and we encourage you to check this website prior to the Annual Meeting if you plan to attend.

Ownership by Insiders

As of the Record Date, our directors and executive officers beneficially owned an aggregate of 660,646289,930 shares of Class A common stock (such number includes shares of common stock that may be issued upon exercise of outstanding options that are currently exercisable or that become exercisable prior to May 8, 2016)23, 2020) and 13,191,84513,187,195 shares of Class B common stock, which together constitute approximately 36.2%33.4% and 84.5%83.1% of the outstanding shares and voting control of our common stock, respectively.

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Solicitation

The Board is making this solicitation of proxies on our behalf. In addition to the solicitation of proxies by use of the mail, our officers and employees may solicit the return of proxies by personal interview, telephone, email or facsimile. We will not pay additional compensation to our officers and employees for their solicitation efforts, but we will reimburse them for any out-of-pocket expenses they incur in their solicitation efforts.

We will request that brokerage houses and other custodians, nominees and fiduciaries forward our solicitation materials to beneficial owners of our common stock. We will bear all costs associated with preparing, assembling, printing and mailing this proxy statement and the accompanying materials, the cost of forwarding our solicitation materials to the beneficial owners of our common stock, and all other costs of solicitation.

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CORPORATE GOVERNANCE

Corporate Governance Guidelines

The Board has established and adopted guidelines that it follows in matters of corporate governance (the Corporate Governance Guidelines). These Corporate Governance Guidelines assist the Board in the exercise of its responsibilities and provide a framework for the efficient operation of our Company, consistent with the best interests of our stockholders and applicable legal and regulatory requirements. The Nominating and Corporate Governance Committee periodically reviews and reassesses the adequacy of our Corporate Governance Guidelines. We have posted a current copy of our Corporate Governance Guidelines, which was last amended in January 2016,2020, on the Corporate Governance page in the Investor Relations section of our website atwww.mantech.com (our(our Website).

Director Independence

The Board comprises a majority of directors who are independent from management. Only independent directors serve on each of our Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee.

The Board has conducted an evaluation of director independence, based on the independence standards applicable to Nasdaq-listed companies and applicable SEC rules and regulations. In the course of the Board’s evaluation of the independence of each non-management director, the Board considered any transactions, relationships and arrangements between such director (or any member of his or her immediate family) and the Company, its subsidiaries and its affiliates. The purpose of this evaluation was to determine whether any relationships or transactions exist that could be inconsistent with a determination by the Board that the director has no relationship that would interfere with his or her exercise of independent judgment in carrying out the responsibilities of a director.

As a result of this evaluation, the Board has affirmatively determined that the following directors nominated for election at the Annual Meeting are independent of the Company and its management under the above referenced standards and regulations:

The Board also affirmatively determined that Stephen W. Porter (who is retiring after the completion of his current Board term) is independent of the Company and its management under the above referenced standards and regulations. The Board determined that Mr. George J. Pedersen our(our Executive Chairman and Chairman of the Board and Chief Executive Officer,Board) is not independent because heof his voting control over the Company’s common stock, his former role as our Chief Executive Officer, and his current role as our Executive Chairman. The Board also determined that Mr. Kevin M. Phillips is employed by the Company.not independent given his role as our President and Chief Executive Officer.

Board Leadership Structure

The Board believes that no single leadership model is right for all companies at all times. Depending on the circumstances, different leadership models might be appropriate. Our Corporate Governance Guidelines do not require that the roles of Chief Executive Officer (CEO)CEO and Chairman of the Board be separate or combined. The Board’s policy as to whether the roles of the CEO and Chairman of the Board should be separate or combined is to adopt the practice that best serves the Company at any given point in time. Currently, our CEO also serves asthe roles of Chairman of the Board.Board and CEO at the Company are separate. The Board considered the appropriateness of the Company’s leadership structure in light of the specific characteristics of the Company (including Mr. Pedersen’s voting control of our common stock and his former service as our CEO). The Board believes this

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the current structure provides an effective and efficient leadership model for the Company at this time, and that combining the rolestime.

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Because our Chairman of the Board fosters clear accountability, effective decision-making and alignment on corporate strategy.

Because we have combined the roles of CEO and Chairman of the Board,is not an independent director, pursuant to our Corporate Governance Guidelines our independent directors have designated one of our independent directors, Mr. Campbell, to serve as the Presiding Director.Company’s presiding independent director (Presiding Director). Mr. Campbell’s duties in this capacityas Presiding Director include:

Board and Committee Executive Sessions and Independent Directors Meetings

The independent directors of the Board regularly meet in executive session, without the presence of management; typically, these sessions are held following the adjournment of certain regularly-scheduled Board meetings. The Board’s independent directors meet no fewer than two times annually. Certain of the Board’s primary standing committees (including the Audit Committee and Compensation Committee) also regularly meet in executive session. As Presiding Director, Mr. Campbell chairs meetings of our independent directors; committee chairpersons preside over executive sessions for their respective committees.

Board’s Role in Risk Oversight

While risk management is a business and operational responsibility of the Company's management team, the Board is responsible for the oversight of the Company's risk management activities. The Board primarily oversees the management of risks inherent in the operation of the Company’s business. The Board oversees the management of risk principally through the Audit Committee. Among other activities, the Audit Committee oversees the Company’s enterprise risk management program. The Board oversees the management of risk relating to certain of the Company’s business activities (particularly those designated as classified by the U.S. government), as well as risks posed by cyber security, information assurance and similar matters, through the Special Programs Oversight Committee. The Board fulfills its responsibility for overseeingand Special Programs Oversight Committee work together on a coordinated basis to oversee the management of risk related to cybersecurity and information assurance matters. The Board oversees the assessment of risks associated with the Company’s compensation policies and programs through the Compensation Committee.

Each of these committees regularly receives reports from, and discusses those reports with, members of management who are responsible for applicable day-to-day risk management functions of the Company. The chairpersons of these committees periodically report back to the Board regarding risk management activities within such committees’ respective purview. The Board’s role in risk oversight has not had any effect on the Board’s leadership structure.

Board and Committee Self-Evaluations

Each of the Board and its primary standing committees (the Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee) conductsperforms a regular, periodic self-evaluation (typically conducted on an annual basis.basis). These evaluations are designed to foster candid discussion regarding the adequacy and effectiveness of the Board and such committees. The Nominating and Corporate Governance Committee oversees the annual self-evaluation process. Where appropriate, the Nominating and Corporate Governance Committee may consider feedback received from the evaluation process in

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making recommendations to the Board regarding the nomination of incumbent directors for re-election to the Board (and, where applicable, assignments of Board members to various committees).

Director Nominations

The Board generally identifies and attracts candidates through its own efforts, and it believes that this method has been effective. However, if in the future the Board determines that it is in the Company’s best interest to use the services of a consultant or a search firm to assist with the identification and selection process, it will do so.

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The Nominating and Corporate Governance Committee is responsible for reviewing the qualifications of potential director nominees, and then recommending director candidates for nomination by the Board.

We do not have a formal policy regarding the consideration of diversity in identifying potential director nominees. However, the Nominating and Corporate Governance Committee considers diversity in its broadest sense when evaluating candidates. Our Corporate Governance Guidelines direct that the evaluation of nominees should include (among numerous other considerations) an assessment of whether a nominee would provide the Board with a diversity of viewpoints, backgrounds, experiences and other demographics.

The Nominating and Corporate Governance Committee has a policy regarding the consideration of director candidates recommended by our stockholders (Nominations Policy). The Nominations Policy describes the circumstances pursuant to which the Nominating and Corporate Governance Committee will consider Board candidates recommended by our stockholders. The Nominations Policy also describes the procedures to be followed by stockholders in submitting such recommendations. We have made the Nominations Policy available on the Corporate Governance page of our Website.

Generally, the Nominating and Corporate Governance Committee will consider candidates recommended by stockholders who beneficially own at least 1% of our outstanding stock at the time of recommendation (Qualifying Stockholder). Qualifying Stockholders wishing to recommend candidates to the Nominating and Corporate Governance Committee may do so by submitting a completed Stockholder Recommendation of Candidate for Director Form (Recommendation Form), which is attached to the Nominations Policy posted on our Website.

Qualifying Stockholders wishing to recommend a nominee for election as director at the next annual meeting of stockholders must submit their completed Recommendation Form at least 120 days in advance of the one-year anniversary of the date of the mailing of this proxy statement. The Nominating and Corporate Governance Committee will only evaluate a candidate if he or she has indicated a willingness to serve as a director and cooperate with the evaluation process, and if the required information about the candidate has been submitted. Candidates recommended by Qualifying Stockholders will generally be evaluated by the Nominating and Corporate Governance Committee pursuant to the same process used for evaluation of all other director candidates.

Code of Ethics

Our The policies in ourStandards of Ethics and Business Conduct satisfy includes a "Financial Code of Ethics" that satisfies the SEC’s requirements for a “codecode of ethics”ethics applicable to our principal executive officer, principal financial officer, principal accounting officer, controller and persons performing similar functions, as well asfunctions. Our Standards of Ethics and Business Conduct also satisfies Nasdaq’s

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requirements for a code of conduct applicable to all directors, officers, and employees. Among other principles, ourStandards of Ethics and Business Conductincludes guidelines relating to the ethical handling of actual or potential conflicts of interest, compliance with laws, accurate financial reporting, and procedures for promoting compliance with (and reporting violations of) such standards. A copy of ourStandards of Ethics and Business Conductis available on the Corporate Governance page of our Website. We are required to disclose any amendment to, or waiver of, a provision of our code"Financial Code of ethics applicable to our principal executive officer, principal financial officer, principal accounting officer, controller or persons performing similar functions.Ethics." We intend to use our Website as a method of disseminating this disclosure, as permitted by applicable SEC rules.

Communication with Directors

We believe that it is important for our stockholders to be able to communicate their concerns to our Board. Stockholders may correspond with any director, committee, or the Board generally, by writing to the following address: ManTech International Corporation Board of Directors, 12015 Lee Jackson Highway, Fairfax,2251 Corporate Park Drive, Herndon, VA 22033-3300,20171, Attention: Corporate Secretary. Please specify to whom your correspondence should be directed. Our Corporate Secretary has been instructed to promptly forward all correspondences to the relevant director, committee, or the full Board, as indicated in your correspondence.

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Director Attendance at Annual Meeting of Stockholders

We invite all of our directors to attend our annual meeting of stockholders, and we strongly encourage all of them to do so absent exigent circumstances that prevent their attendance. In furtherance of this policy, we generally schedule one of our regular Board meetings on the same day as our annual meeting of stockholders. In 2015, seven2019, all of the eightour directors then serving on the Board attended our annual meeting of stockholders.

Availability of Corporate Governance Documents

We have made available on the Corporate Governance page of our Website a number of important documents related to our governance practices, including:

We will also make these materials available in print format to any requesting stockholder. Copies of these documents may be requested by writing to the following address: ManTech International Corporation, 12015 Lee Jackson Highway, Fairfax,2251 Corporate Park Drive, Herndon, VA 22033-3300,20171, Attention: Corporate Secretary.

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BOARD OF DIRECTORS

AND COMMITTEES OF THE BOARD OF DIRECTORS

Our Board currently comprises eight members each of whom was elected at the 2015 Annual Meeting of Stockholders for a term that expires at the Annual Meeting. All of the directors were elected at the 2019 Annual Meeting of Shareholders. Set forth below are details regarding director attendance at board and committee meetings, the function and operation of each of the Board’s standing committees, and the compensation of our non-employee directors in 2015.2019.

Attendance at Board and Committee Meetings

Our full Board met eightsix times in 2015. Each2019. All of our directors attended or participated in at least 75% of the aggregate of the board meetings and the meetings of the committees on which the director served during 2015.2019. The number of meetings held in 20152019 by each of the Board’s standing committees is set forth in the information below.

Committees of the Board

The Board currently has six standing committees (although the Board may establish other committees from time to time). The following table sets forth the current composition of our Board committees.

Certain information regarding each standing Board committee is provided below. A more detailed discussion of each committee’s composition, purpose, objectives, authority and responsibilities can be found in its charter, which we make available on the Corporate Governance page of our Website.

Audit Committee

The primary functions of the Audit Committee are to oversee (i) the integrity of our financial statements, (ii) our accounting and financial reporting processes, and (iii) audits of our financial statements. The Audit Committee operates under a written charter thatand it reviews and reassesses the adequacy of that charter on an annual basis. The charter was most recently revised and amended in March 2016 and is available on our Website.

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The Board annually reviews the suitability of our Audit Committee in light of the Nasdaq listing standards’ requirements for audit committee composition and applicable SEC rules and regulations. The Board has determined that each member of our Audit Committee meets the heightened independence standard and other

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requirements for audit committee members under applicable Nasdaq listing standards and SEC rules and regulations.

The Board has also determined that the Company has at least one audit committee financial expert serving on the Audit Committee. The Board has determined that each of Messrs.Mr. Campbell and Fatzinger and Ms. Bush (i) qualifies as an “audit committee financial expert” under applicable SEC rules and regulations, and (ii) satisfies the financial sophistication requirements of the Nasdaq listing standards. All of our Audit Committee members have a working familiarity with basic finance and accounting practices.

During 2015,2019, the Audit Committee held five meetings. The Audit Committee meets regularly in executive session, including with our independent registered public accounting firm, without management present. Mr. Campbell serves as chairperson of the Audit Committee.

Compensation Committee

The primary functions of the Compensation Committee are to (i) oversee the determination, implementation, and administration of the remuneration (including salary, incentive compensation payments, bonuses, equity compensation, and perquisites) of all non-employee directors and executive officers of the Company, (ii) review and approve or ratify all equity grants, and (iii)(ii) administer the Company’s stock-based compensation plans. The Compensation Committee operates under a written charter, thatand it reviews and reassesses the adequacy of that charter on an annual basis. The charter was most recently revised and amended in February 20142019 and is available on our Website.

The Board annually reviews the suitability of our Compensation Committee in light of the Nasdaq listing standards’ requirements for compensation committee composition and applicable SEC rules and regulations. The Board has determined that each member of our Compensation Committee meets the independence and other requirements for compensation committee members under applicable Nasdaq listing standards and SEC rules and regulations. Our Compensation Committee members also qualify as “non-employee directors” under Section 16 of the Securities Exchange Act of 1934 (the Exchange Act) and as “outside directors” under Section 162(m) of the Internal Revenue Code..

During 2015,2019, the Compensation Committee held four meetings. At the direction of the Compensation Committee, certain members of management attend each meeting.most meetings. The Compensation Committee also meets regularly in executive session without management present. Mr. FatzingerCampbell serves as chairperson of the Compensation Committee.

The Compensation Committee has the authority, in its sole discretion, to retain or obtain the advice of compensation consultants, legal counsel or other advisers, and is directly responsible for the appointment, compensation and oversight of the work of any such adviser. The Compensation Committee conducts an independence assessment of any compensation adviser it engages; such assessment includes the consideration of the factors required by applicable Nasdaq listing standards and SEC rules and regulations.

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For 2015,2019, the Compensation Committee retained Ernst & Young LLP (E&Y)(EY) as its independent compensation consultant to assist the Compensation Committee with its executive compensation-related responsibilities. The services provided by E&YEY in its capacity as the Compensation Committee’s independent compensation consultant included supporting the design of our executive compensation program, providing market consensus data for each of our executive officers, and assisting the Compensation Committee in evaluating the compensation of our non-employee directors.

From time to time, with the consent of the Compensation Committee, the Company’s management has retained personnel at E&YEY to perform services that are not related to work performed as the Compensation Committee’s independent compensation consultant (Additional Services), for which E&YEY receives a fee. The Compensation Committee has approved the Company’s future use of E&YEY for certain projects, including due diligence support for acquisitions or other corporate transactions, tax advisory services, consulting and advisory services with respect to the Company’s internal systems and, as directed by the chairperson of the

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Compensation Committee, consulting and advisory services related to compensation of the Company’s non-executive officers. The Company’s management did not engage E&YEY to perform Additional Services in 2015.2019.

Based on its review of these relationships, and independence and other factors that the Compensation Committee determines to be relevant, as well as policies and procedures implemented by the Compensation Committee and E&Y,EY, the Compensation Committee has concluded that the compensation consulting advice it receives from E&YEY is objective, and that no conflicts of interest exist that would require disclosure by the Company under applicable SEC rules.

The Company’s processes and procedures for the consideration and determination of director and executive compensation (including the roles of the Compensation Committee, management, and the Compensation Committee’s independent compensation consultant) are discussed in the sections of this proxy statement captioned “Setting Compensation of Non-Employee Directors” and “Compensation Discussion and Analysis,” respectively.

Nominating and Corporate Governance Committee

The primary functions of the Nominating and Corporate Governance Committee are to (i) identify individuals qualified to become members of the Board, and recommend new director candidates to the Board when necessary and appropriate, (ii) evaluate whether incumbent directors should be nominated for re-election to the Board and make recommendations to the Board in this regard, and (iii) oversee and periodically evaluate certain of the Company’s corporate governance policies and procedures.Corporate Governance Guidelines. The Nominating and Corporate Governance Committee operates under a written charter, thatand it reviews and reassesses the adequacy of that charter on an annual basis. The charter was most recently revised and amended in March 2016 and is available on our Website. All members of the Nominating and Corporate Governance Committee are independent directors, within the meaning of applicable Nasdaq listing standards and SEC rules and regulations. The Nominating and Corporate Governance Committee held twothree meetings in 2015.2019. Mr. Porter currentlyArmitage serves as chairperson of the Nominating and Corporate Governance Committee.

Retirement Plan Committee

The primary function of the Retirement Plan Committee is to oversee the administration of the Company’s tax-qualified and non-qualified retirement plans. The Retirement Plan Committee held sixfive meetings in 2015. Mr. Fatzinger2019. Ms. Bush serves as chairperson of the Retirement Plan Committee.

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Special Programs Oversight Committee

The Special Programs Oversight Committee oversees certain of the Company’s business activities (particularly those designated as classified by the United States government for purposes of national security), as well as cyber security,and works with the Board to oversee the management of risks related to cybersecurity or information assurance and similar matters that have the potential for posing significant risk to the Company.matters. The Special Programs Oversight Committee held twofour meetings in 2015.2019. Mr. Kerr serves as chairperson of the Special Programs Oversight Committee.

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The primary function

Table of the Executive Committee is to assist the Board in fulfilling its oversight responsibilities. The Executive Committee is authorized to exercise the powers of the Board in managing the affairs of the Company during intervals between Board meetings, when Board action is necessary or desirable but convening a special Board meeting is not warranted or practical. The Executive Committee did not meet in 2015. Mr. Pedersen serves as chairperson of the Executive Committee.Contents

Setting Compensation of Non-Employee Directors

Our Compensation Committee sets compensation for the Company’s non-employee directors. The Compensation Committee generally reviews non-employee director compensation on an annual basis. In conducting this review, the Compensation Committee receives input on market trends for non-employee director compensation from its independent compensation consultant, including with respect to the Company’s compensation peer group (as set forth in the “Compensation Discussion & Analysis” section of this proxy statement); however, the Compensation Committee does not target non-employee director compensation at any particular percentile or percentile range of the market data. A substantial portion of the non-employee directors’ compensation is payable in the form of stock-based compensation, in order to align the interests of the directors with those of the Company’s stockholders.

We do not compensate Mr. Pedersen or Mr. Phillips for his service on the Board or any committee of the Board. In certain circumstances, members of the Board may receive reimbursement for certain expenses incurred in connection with attending Board or committee meetings. For the current Board term (which began in May 2015)2019), the Compensation Committee decided not to make any changes to non-employee directorequity amounts and cash compensation levels (both with respect to cash and equity)remained unchanged from those levels applicable to the prior Board term.term, with the exception of a small increase in the amount of the annual retainers that we pay to each of the chairperson of our Nomination and Corporate Governance Committee and our Special Program Oversight Committee. The compensation we paid in 20152019 to our non-employee directors for their services is set forth in the table that follows.

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NON-EMPLOYEE DIRECTOR COMPENSATION TABLE

The tables and footnotes below reflect the compensation and other fees paid in 20152019 to our non-employee directors for their services.

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PROPOSAL 1

ELECTION OF DIRECTORS

General Information

The Board has nominated sevenall of the Company’s eight current directors to serve as a director until the 20172021 Annual Meeting of Stockholders, or until their respective successors have been duly elected and qualified. Mr. Stephen Porter is retiring after the completion of his current Board term. Each nominee is a current member of the Board, has agreed to stand for election and serve if elected, and has consented to be named in this proxy statement.

Substitute Nominees

If any nominee should become unavailable for election or is unable to be a candidate when the election takes place (or otherwise declines to serve), the persons named as proxies may use the discretionary authority provided to them in the proxy to vote for a substitute nominee designated by the Board. At this time, we do not anticipate that any nominee will be unable to be a candidate for election or will otherwise decline to serve.

Vacancies

Under our SecondThird Amended and Restated Bylaws, the Board has the authority to fill any vacancies that arise, including vacancies created by an increase in the number of directors, or vacancies created by the resignation of a director. Any nominee so elected and appointed by the Board would hold office for the remainder of the term of office of all directors, which term expires annually at our annual meeting of stockholders, or until his successor is duly elected and qualified.

Information Regarding the Nominees for Election as Directors

The name and age (as of the Mailing Date) of each nominee for election as director, as well as certain additional information concerning each nominee’s principal occupation, other affiliations, and business experience during the last five years, are set forth below.

The Board has concluded that each of the incumbent directors (other than Mr. Porter, who is retiring after the completion of his current Board term) should be nominated for re-election based on the specific experience, qualifications, attributes and skills identified in the biographical information below, in light of the Company’s business and structure.

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Mr. Pedersen is athe Company’s co-founder, Executive Chairman and Chairman of the Board and Chief Executive Officer of the Company.Board. Mr. Pedersen has served as a director of ManTech since 1968, was appointed1968. He has served as Chairman of the Board in 1979, and was named Chief Executive Officer in 1995.since 1979. Mr. Pedersen waspreviously served as the Company’s CEO until the end of 2017. He also served as President of the Company from 1995 until 2004. Until 2011,In the past, Mr. Pedersen served on the board of directors of GSE Systems, Inc. (NYSE Amex: GVP), which provides simulation, training and engineering solutions to the energy and process industries. Mr. Pedersen has also served on the board of directors of various public and private companies and industry associations.

Qualifications

Mr. Pedersen’sPedersen's unparalleled knowledge of the Company and its operations, and his experience in providing innovative technologies and solutions for mission-critical national security programs to U.S. government customers for almost half a century, uniquely positions him to serve as the Company’s Executive Chairman and Chairman of the Board and Chief Executive Officer.Board. In addition to his operational experience, Mr. Pedersen has an in-depth knowledge and understanding of the U.S. government’s mission requirements and related funding priorities.

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Mr. Armitage has served as a director of ManTech since 2005. From 1995 to 2001, Mr. Armitage served on our Advisory Board. Since 2005, Mr. Armitage has served as President of Armitage International, L.C., which provides multinational clients with critical support in the areas of international business development, strategic planning, and problem-solving. From 2001 through 2005, he served as the Deputy Secretary of State, and prior to that assignment he was President of Armitage Associates, L.C., a world-wide business and public policy firm. Beginning in the late 1980’s,1980s, Mr. Armitage held a variety of high-ranking diplomatic positions, including as Presidential Special Negotiator for the Philippines Military Bases Agreement; as Special Mediator for Water in the Middle East; as a Special Emissary to Jordan’s King Hussein during the 1991 Gulf War; and as an Ambassador, directing U.S. assistance to the new independent states of the former Soviet Union. Mr. Armitage is also a former Assistant Secretary of Defense for International Security Affairs, and a former Assistant Secretary of Defense for East Asia and Pacific Affairs. Mr. Armitage has received numerous U.S. military decorations, has been awarded the Department of Defense Medal for Distinguished Public Service four times, and has received the Presidential Citizens Medal and the Department of State Distinguished Honor Award. In 2005, he was awarded a KBE and became a Knight Commander of the Order of St. Michael and St. George. Mr. Armitage was also appointed as an honorary companion to the Order of Australia (Australian Knighthood) and an honorary companion of the New Zealand Order of Merit. In November 2015, Mr. Armitage was awarded the Grand Cordon of the Order of the Rising Sun from Japan. Mr. Armitage currently servesserved on the board of directors of ConocoPhillips (NYSE: COP), which is one of the largest integrated energy companies in the United States.States, from 2006 to 2018.

Qualifications

Mr. Armitage brings to the Board significant leadership experience and industry expertise. Mr. Armitage has worked in the highest levels of the U.S. government, providing him with critical insight into the needs and operations of U.S. government intelligence, military, and civilian agencies, and other matters relating to foreign affairs. His many years of combined service on our Board and our Advisory Board, as well as his service on the boards of directors of other public and private companies, give him a significant understanding of the role of the Board and knowledge of the Company and its operations.

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Ms. Bush has served as a director of ManTech since 2006. In 1991, Ms. Bush founded Bush International, a global consulting firm which advises U.S. companies and foreign governments on international financial markets and banking, and global business strategy. Ms. Bush also serves as a senior managing director of Brock Capital Group, a corporate advisory and consulting firm. In 2007, she was appointed by the Secretary of the Treasury to the U.S. Treasury Advisory Committee on the Auditing Profession. From 1989 to 1991, Ms. Bush served as Managing Director and Head of the Federal Housing Finance Board, the oversight body for the nation’s 12 Federal Home Loan Banks. Prior to 1989, Ms. Bush was the Vice President and Head of International Finance at the Federal National Mortgage Association (Fannie Mae). From 1982 to 1984, Ms. Bush served as U.S. Alternate Executive Director of the International Monetary Fund (IMF), a position appointed by the President of the United States and confirmed by the Senate. In that capacity, she worked with the U.S. Treasury Department to formulate policy on IMF lending and global economic matters. Ms. Bush currently serves on the boardboards of directors of Discover Financial Services (NYSE: DFS), Marriott International, Inc. (NYSE: MAR), and the T. Rowe Price Group (NASDAQ: TROW) and Bloom Energy (NYSE:BE).*

*Ms. Bush also previously servedhas informed the Board that she will be retiring from one of her other public company boards (as she has reached the mandatory retirement age applicable for such board), and will no longer serve on such board after May 2020, bringing the number of public company boards on which she serves to three (in addition to the serving on the boardsCompany's Board).

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Table of directors of United Airlines (NYSE: UAL), Brady Corporation (NYSE: BRC), Briggs & Stratton Corporation (NYSE: BGG), MGIC Investment Corporation (NYSE: MTG), and the Pioneer Family of Mutual Funds.Contents

Qualifications

As an experienced financial and operational leader of numerous high profilehigh-profile institutions in a variety of industries, Ms. Bush brings a broad understanding of the operations and business and economic challenges of public companies. Ms. Bush has chaired or served on all significant standing committees of public company boards during her career. Ms. Bush has deep knowledge of financial, investment, and governance matters, and received her MBA in finance from the University of Chicago. Her background and experience, including her experience with public policy matters and providing strategic advisory services in political and international arenas, coupled with her service and leadership in government, afford Ms. Bush with a valuable perspective for service on our Board.

Mr. Campbell has served as a director of ManTech since 2002. From 1999 to 2001, Mr. Campbell served as a director, President and Chief Executive Officer of Allied Aerospace Industries, Inc., a Virginia-based aerospace and defense engineering firm. From 1993 to 1997, Mr. Campbell served as President and Chief Executive Officer of Vitro Corporation, the largest subsidiary of Tracor, Inc. InBeginning in 1997, he served as Chairman and Chief Executive Officer of Tracor’s subsidiary, Tracor Systems Technologies, Inc. until the sale of Tracor, Inc. to GEC Marconi, plc in 1998.

Qualifications

As a former senior executive of public companies and companies in our industry, Mr. Campbell brings management experience, leadership capabilities, financial knowledge, and business acumen to our Board. Mr. Campbell has a deep understanding of the Company and its operations, having served on our Board for over a decadesince our initial public offering and chaired our Audit Committee since 2004. Mr. Campbell’s knowledge of our Company, and his financial and operational experience leading comparable companies in our industry through challenges and opportunities that we regularly face, make him a valued and important contributor to our Board.

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Mr. Fatzinger has served as a director of ManTech since 2002. Mr. Fatzinger served as Executive Vice President of Chevy Chase Bank, F.S.B., the parent of ASB Capital Management, Inc., from 1999 to 2002. Mr. Fatzinger currently serves as a director of both Chevy Chase Trust Company and ASB Capital Management, where he is Chairman of the Audit Committee and the Real Estate Investment Activities Committee, and is Chairman Emeritus of the University of Maryland Foundation. Mr. Fatzinger also previously served on the board of directors of Optelecom, Inc., which was a Nasdaq listed company prior to its sale in 2011.

As a former leader of high-profile companies in the financial industry, Mr. Fatzinger brings to the Board a broad range of capabilities relating to the management, operation, and financial performance of companies. He has led and overseen institutions throughout the many stages of a company’s lifecycle. Mr. Fatzinger also has a deep understanding of the Company and its operations, having served on our Board for more than ten years and chaired our Compensation Committee since 2004. This knowledge and his financial and operational experience make him a valued and important contributor to our Board.

Mr. Kerr has served as a director of ManTech since 2002. From 1994 to 2002, Mr. Kerr served as Chairman of our Advisory Board. From 1996 to 2001, Mr. Kerr served as President of the Security Affairs Support Association, an organization comprising government and industry members that is focused on national security policy. Prior to that, Mr. Kerr worked at the Central Intelligence Agency for 32 years, including as Deputy Director for Central Intelligence. Mr. Kerr headed a small team that assessed intelligence produced prior to the Iraq war, at the request of the Secretary of Defense and Director of Central Intelligence. For seven years Mr. Kerr currently servesserved on the boardIndependent Monitoring Commission that monitored the Good Friday Agreement in Northern Ireland. Mr. Kerr has previously served on the boards of directors of BAE Systems, Inc., a subsidiary of BAE Systems plc. He also previously served on the boards of directors ofplc, MITRE Corporation and LexisNexis.

Qualifications

Mr. Kerr brings to the Board significant leadership experience and industry knowledge, particularly within the intelligence community. His continued involvement in the formation of the nation’s security policies has ensured his continued expertise in this area. His many years of combined service on our Board and our Advisory Board, as well as his service on the board of directors of other high-profile companies in our industry, gives him a significant understanding of the role of the Board, and knowledge of the Company, its operations, and the markets it serves. His familiarity with and knowledge of issues relating to the operation of certain Company business activities involving programs designated as classified by the U.S. government and his understanding of cyber security risks give him the background to chair our Special Programs Oversight Committee.

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Mr. LaMontagne has served as a director of ManTech since 2019. From March 2019 until its sale to NV5 Global, Inc. in December 2019, Mr. LaMontagne served as the president and chief executive officer of Quantum Spatial, an end-to-end geospatial services company that works with government and corporate organizations to mitigate risk, better manage resources, drive growth and gain new understandings. In addition, since April 2019, Mr. LaMontagne has served as an operating advisor to M33 Growth, a Boston-based growth equity fund focused on tech services and software investments, assisting M33 in reviewing acquisition targets and developing investment theses. From November 2018 to December 2019, Mr. LaMontagne served as an advisor to Arlington Capital Partners, a private equity firm. From 2012 to 2017, Mr. LaMontagne served as chief executive officer of Novetta Solutions, an advanced analytics technology solutions company, and from 2006 to 2011, served as president and chief executive officer of Paradigm Solutions Corporation, a cyber security and digital forensics firm. Prior to beginning his career in technology-focused businesses, Mr. LaMontagne served as U.S. Foreign Service Officer with the U.S. Department of State, specializing in China and East Asia political and economic affairs, including a posting at the U.S. Embassy in Beijing, China. Mr. LaMontagne currently serves on the board of directors of several private companies.

Qualifications

Mr. LaMontagne brings significant management, leadership capabilities and cyber security and other industry experience to our Board. Mr. LaMontagne also has familiarity with the Company’s operations, having served as an executive at the Company from 1999 to 2006, during which time he helped execute Company’s growth strategy, initial public offering, and expansion into the intelligence community. Mr. LaMontagne’s knowledge of national security and his technology solutions expertise in the federal and commercial arenas, make him a valued contributor to the Board and our Special Programs Oversight Committee.

Lieutenant General Minihan (Retired) has served as a director of ManTech since 2006. Since 2002, Lieutenant General Minihan has served as Managing Director of the Homeland Security Fund for Paladin Capital Group. From 1999-2002, Lieutenant General Minihan served as President of the Security Affairs Support Association. Lieutenant General Minihan served for over thirty years in the Air Force, serving from 1996 to 1999 as the 14th Director of the National Security Agency/Central Security Service. From 1995 to 1996, he was a Director of the Defense Intelligence Agency. Among Lieutenant General Minihan’s awards and decorations are the National Security Medal, the Defense Distinguished Service Medal, the Bronze Star, the National Intelligence Distinguished Service Medal, and the Legion of Merit. Lieutenant General Minihan is a founder of the Intelligence and National Security Alliance in Washington, D.C., and serves on the boards of directors of KEYW Corporation (NASDAQ: KEYW), CGI Federal, a subsidiary of CGI Group Inc., and Lexis Nexis Special Services Inc. He also is a former member of the board of directors of Verint Systems, Inc. (NASDAQ: VRNT), BAE Systems, Inc., a subsidiary of BAE Systems plcplc. and MTC Technologies, Inc., which was a Nasdaq listed companyKEYW Corporation prior to its sale.acquisition by Jacobs Engineering Group Inc (NSYE:JEC) in 2019.

Qualifications

Lieutenant General Minihan brings to the Board an impressive mix of military, government, business, and investment experience in the Company’s industry. His position as Managing Director of the Homeland Security Fund for Paladin Capital Group also gives Lieutenant General Minihan keen insight into merger and acquisition activity within our industry. Lieutenant General Minihan’s industry knowledge is supplemented by his experience serving on numerous other public and private company boards in the defense and government IT services industry, and as a result he has deep understanding of the role of the Board and the Company, as well as the Company’s addressable markets.

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Mr. Phillips has served as Chief Executive Officer of ManTech and as a member of the board since 2018. Prior to his appointment as our Chief Executive Officer, Mr. Phillips served as the Company’s President and Chief Operating Officer from 2016 to 2017. From 2005 to 2016, Mr. Phillips served as the Company’s Chief Financial officer. Before that, Mr. Phillips served as the Company’s corporate vice president and assistant to the chairman and chief of staff. Mr. Phillips joined the Company in December 2002, when CTX Corporation was acquired by ManTech. Mr. Phillips had served as the chief financial officer of CTX Corporation. Mr. Phillips serves on the board of directors of Northern Virginia Technology Council (NVTC), a technology trade association, and the board of directors of Aerospace Industries Association (AIA).

Qualifications

As an experienced financial and operational expert for government IT service providers, Mr. Phillips brings his broad and deep experience and industry knowledge to his service on the Board. Mr. Phillips has served in senior financial and strategic roles with multiple IT service providers to the government for almost 25 years. Specifically with respect to ManTech, Mr. Phillips has a deep understanding of the Company and its operations, and has lead the development of the Company’s strategic vision to drive ManTech’s growth.

Recommendation of the Board of Directors

The Board recommends that you vote “FOR” the election of each of the director nominees listed above. All proxies executed and returned will be voted “FOR” all of the director nominees unless the proxy specifies otherwise.

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EXECUTIVE OFFICERS

We have set forth below the positions, names and ages (as of the Mailing Date) of our current executive officers (other than George Pedersen, our CEOExecutive Chairman and Chairman of the Board)Board, and Kevin Phillips, our President and CEO). Biographical information for each of our executive officers is also presented below. The biographical and other required information for each of Mr. Pedersen and Mr. Phillips is presented in the section of this proxy statement captioned “Information Regarding the Nominees for Election as Directors.”"

Our executive officers serve at the discretion of the Board.

Ms. Bjornaas has served as our Chief Financial Officer since November 2016. Ms. Bjornaas served as the Company’s Senior Vice President of Financial Planning and Analysis and Deputy Chief Financial Officer from December 2010 until November 2016. Ms. Bjornaas assumed the duties and responsibilities of the Company’s principal accounting officer in August 2012. Prior to joining ManTech, she was the chief financial officer of NCI, Inc., a public company that provided information technology and professional services and solutions to federal government agencies.

Matt Tait has served as president of ManTech’s Mission Solutions and Services (MSS) business group since July 2018. Before joining the Company in 2018, Mr. Tait held various positions at Accenture plc (NSYE: ACN), a $20 billion Fortune Global 500 company, for almost 20 years, where he most recently served as Senior Managing Director and Defense lead, where he led initiatives that transformed IT performance for customers in defense, federal civilian, health care and financial sectors. Prior to his time at Accenture, Mr. Tait served ten years as an officer in the U.S. Navy.

Rick Wagner has served as president of ManTech’s Mission, Cyber & Intelligence Solutions (MCIS) business group since January 2018. From 2015 through 2017, Mr. Wagner served as the Executive Vice President and Chief Operating Officer of MCIS, leading the group’s day-to-day operations, and before that as Senior Vice President ManTech’s Advanced Technology Solutions business. Before joining ManTech in 2015, Mr. Wagner was chief strategy officer at TASC, Inc., where he led merger and acquisition activity, including due diligence and integration for the merger with Engility Holdings, Inc. During his 16 years at TASC, Mr. Wagner held positions of increasing responsibility from program, and line management before becoming a senior executive.