Exhibit 99.1

Investor Relations Stuart Davis (703) 218-8269 stuart.davis@mantech.com

ManTech Announces Financial Results for

Fourth Quarter and Fiscal Year 2011

FAIRFAX, Va. – Feb. 22, 2012 – ManTech International Corporation (NASDAQ:MANT) (www.mantech.com), a leading provider of innovative technologies and solutions for mission-critical national security programs, today announced financial results for the fourth quarter and fiscal year 2011, which ended Dec. 31, 2011.

“Fiscal year 2011 was an excellent year for ManTech, marked by double-digit revenue growth, increased profits, excellent cash flow, solid contract awards and the implementation of a regular dividend program to provide our shareholders with a compelling value proposition” said ManTech Chairman and Chief Executive Officer George J. Pedersen. “As a result of our disciplined focus on cash, we generated record operating cash flow of $221 million for the year, which enables us to continue our robust acquisition program. The recent acquisitions of WINS and Evolvent enhance our positioning in faster growing market segments, such as information technology and cyber security for the intelligence and federal health care communities. We are confident that ManTech can continue to thrive even as federal spending slows because of our current positioning in cyber security, C4ISR, intelligence and other priority missions and access to more than 1,000 active contracts as well as our ability to target new growth markets with our strong balance sheet and proven history in identifying, executing and integrating acquisitions.”

Beginning in 2012, the company intends to pay dividends quarterly rather than semi-annually. The Board of Directors has declared a cash dividend of $0.21 per share, which will be paid on March 23, 2012 to all common stockholders of record as of March 9, 2012. ManTech anticipates paying equivalent quarterly dividends near the end of each fiscal quarter. Based on the current number of outstanding shares, the anticipated total dividend for 2012 of $0.84 per share of common stock implies a payout of $31 million. The annual yield is approximately 2 ¹/2 percent based on the closing price on February 21, 2012. Future declarations of quarterly dividends and their record and payment dates are subject to the final determination of ManTech’s Board of Directors.

Summary Operating Results

Revenues for the year were $2.87 billion, up about 10 percent from $2.60 billion in fiscal year 2010. Revenues for the quarter were $681.8 million, down 2 percent compared to the fourth quarter of fiscal year 2010. Quarterly revenues increased across most of the company’s core business, especially in certain mobile communications and cyber security programs.

Operating income was $227.4 million for the full year and $53.8 million for the quarter. Operating margin of 7.9 percent for the quarter and the year was in-line with expectations.

Quarterly and annual changes in net income and earnings per share changes were in-line with changes in operating income, as net interest payments, other income and effective tax rate were neutral to earnings and share dilution was modest. Net income was $133.3 million for the year and $30.5 million for the quarter. Diluted earnings per share were $3.63 for the year and $0.83 for the quarter.

Cash Management and Capital Deployment

Cash flow from operations was $221 million for the fiscal year (1.7 times net income) and $43 million (1.4 times net income) for the quarter. The record cash flow for the year benefited from positive payment terms on a mobile cell tower program. Days sales outstanding (DSO) were 71 days for the quarter and the year.

The company invested $90 million in the quarter to acquire Worldwide Information Network Systems, Inc. (WINS), a leading provider of information technology services to the Defense Intelligence Agency (DIA), the Department of State and other government and commercial customers. The company expects to drive strong growth through the WINS prime position on the DIA Solutions for the Information Technology Enterprise (SITE) contract.

As of Dec. 31, 2011, the company had $114 million in cash and cash equivalents and $200 million in debt with no borrowings on its $500 million revolving-credit facility.

After the close of the quarter, the company acquired Evolvent Technologies Inc., a leading federal healthcare systems integrator whose systems and processes enable better decision-making at the point of care and full integration of medical information across different platforms. ManTech expects Evolvent to contribute solid growth and operating margins and be accretive to earnings per share in 2012. After closing, Evolvent received a prime contract to provide management and professional support services for Air Force Medical Service on a five-year, $958 million multiple-award indefinite-delivery/indefinite-quantity (IDIQ) contract.

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Contract Awards

Contract awards (bookings) totaled $907 million in the fourth quarter, representing a book-to-bill ratio of 1.3. For the year contract awards totaled $3.0 billion for a book-to-bill ratio of 1.0. Large awards contributing to the quarterly bookings include:

As a result of strong quarterly awards, the company’s backlog of business at the end of quarter was $4.7 billion, which was up 8% over the previous quarter. Funded backlog was $1.3 billion. The company expects to sustain strong contract award activity again in fiscal year 2012 considering extremely high levels of proposal activity and submitted awards awaiting adjudication.

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Forward Guidance

ManTech enters fiscal year 2012 with a healthy backlog and a strong market position, and the company expects to achieve revenue, net income and diluted earnings per share as specified in the table below.

ManTech Chief Financial Officer Kevin M. Phillips said, “We expect to post robust growth in fiscal year 2012. We believe that our positioning in priority areas will allow us to grow and take market share. The unprecedented level of proposal activity gives us optimism despite market headwinds and uncertainty around sequestration and the government fiscal year 2013 appropriations process. We also intend to maintain our aggressive but disciplined acquisition program to contribute to 2012 financial performance.”

Conference Call

ManTech executive management will hold a conference call on February 22, 2012, at 5 p.m. Eastern to discuss the financial results and outlook and answer questions. Analysts may participate on the conference call by dialing 888-690-2873 (domestic) or 913-312-1443 (international) and entering passcode 2870414. The conference call will be webcast simultaneously to the public through a link on the Investor Relations section of the ManTech website (http://investor.mantech.com).

A replay of the conference call will be available by telephone approximately two hours after the conclusion of the call through March 7, 2012, by dialing 888-203-1112 (domestic) or 719-457-0820 (international) and entering passcode 2870414. In addition, a replay of the webcast will be available on the ManTech website approximately two hours after the conclusion of the conference call.

About ManTech International Corporation

ManTech is a leading provider of innovative technologies and solutions for mission-critical national security programs for the intelligence community; the departments of Defense, State, Homeland Security, Energy and Justice, including the Federal Bureau of Investigation; the space community; and other U.S. federal government customers. We provide support to critical national security programs for approximately 60 federal agencies through approximately 1,000 current contracts. ManTech’s expertise includes command, control, communications, computers, intelligence, surveillance and reconnaissance (C4ISR) lifecycle support, cyber security, global logistics support, intelligence/counter-intelligence support, information technology modernization and sustainment, systems engineering, and test and evaluation. ManTech supports major national missions, such as military readiness, terrorist threat detection, information security and border protection. Additional information on ManTech can be found at www.mantech.com.

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Forward-Looking Information

Statements and assumptions made in this press release, which do not address historical facts, constitute “forward-looking” statements that ManTech believes to be within the definition in the Private Securities Litigation Reform Act of 1995 and involve risks and uncertainties, many of which are outside of our control. Words such as “may,” “will,” “expect”, “intend,” “anticipate,” “believe,” “estimate,” or “continue,” or the negative of these terms or words of similar import are intended to identify forward-looking statements.

These forward-looking statements are inherently subject to risks and uncertainties, and actual results and outcomes may differ materially from the results and outcomes we anticipate. Factors that could cause actual results to differ materially from the results we anticipate, include, but are not limited to, the following: adverse changes in U.S. government spending priorities; failure to retain existing U.S. government contracts, win new contracts or win recompetes; adverse changes in future levels of expenditures for programs we support caused by budgetary pressures facing the federal government and changing mission priorities; failure to obtain option awards, task orders or funding under contracts; failure to maintain strong relationships with other contractors; adverse changes in our mix of contract types; adverse results of U.S. government audits of our government contracts; risk of contract performance, modification or termination; risks associated with complex U.S. government procurement laws and regulations; risks of financing, such as increases in interest rates and restrictions imposed by our outstanding indebtedness, including the ability to meet financial covenants, and risks related to an inability to obtain new or additional financing; failure to successfully integrate recently acquired companies or businesses into our operations or to realize any accretive or synergistic effects from such acquisitions; failure to identify, execute or effectively integrate future acquisitions; and competition. These and other risk factors are more fully discussed in the section entitled “Risks Factors” in ManTech’s Annual Report on Form 10-K previously filed with the Securities and Exchange Commission on Feb. 25, 2011, Item 1A of Part II of our Quarterly Reports on Form 10-Q, and, from time to time, in ManTech’s other filings with the Securities and Exchange Commission.

The forward-looking statements included herein are only made as of the date of this press release, and ManTech undertakes no obligation to publicly update any of the forward-looking statements made herein, whether as a result of new information, subsequent events or circumstances, changes in expectations or otherwise.

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MANTECH INTERNATIONAL CORPORATION

CONSOLIDATED BALANCE SHEETS

(Dollars in Thousands, Except Share Amounts)

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MANTECH INTERNATIONAL CORPORATION

CONSOLIDATED STATEMENTS OF INCOME

(In Thousands Except Per Share Amounts)

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MANTECH INTERNATIONAL CORPORATION

CONSOLIDATED STATEMENTS OF CASH FLOWS

(In Thousands)

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