Amentum Wins Defense Threat Reduction Agency (DTRA) Prime Contract

Company’s Advanced Engineering Solutions to Mitigate Threats Worldwide

CHANTILLY, VA., December 11, 2025 — Amentum (NYSE: AMTM), a leading provider of mission-focused advanced engineering and technology solutions, has been selected as a prime contractor on the $3.5 billion Defense Threat Reduction Agency’s (DTRA) Cooperative Threat Reduction Integrating Contract (CTRIC) IV. As one of six awardees, Amentum will deliver sustainable chemical, biological, radiological, and nuclear threat reduction capabilities to partner nations worldwide.

“Amentum remains steadfast in our mission to protect and preserve global security by delivering expertise in engineering, logistics, and program management,” said Mark Whitney, president of Amentum’s Energy & Environment business. “We will deploy advanced technologies, advanced risk assessment, and mitigation planning to build sustainable local programs that raise resilience. Our team is working closely with DTRA and partner nations to strengthen their ability to prevent, detect, and respond in support of national security.”

Under the 10-year contract Amentum will compete for task orders to deliver a broad range of services and products for DTRA.

The Defense Threat Reduction Agency provides cross-cutting solutions to enable the Department of Defense, the United States government, and international partners to deter strategic attacks against the U.S. and its allies; prevent, reduce, and counter weapons of mass destruction (WMD) and emerging threats; and prevail against WMD-armed adversaries in crisis and conflict.

About Amentum

Amentum is a global leader in advanced engineering and innovative technology solutions, trusted by the United States and its allies to address their most significant and complex challenges in science, security and sustainability. Our people apply undaunted curiosity, relentless ambition and boundless imagination to challenge convention and drive progress. Our commitments are underpinned by the belief that safety, collaboration and well-being are integral to success. Headquartered in Chantilly, Virginia, we have approximately 50,000 employees in more than 70 countries across all 7 continents.

Visit us at www.amentum.com to learn how we advance the future together.

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Media Contact:

Keith Wood

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Investor Contact:

Nathan Rutledge

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Forward-Looking Statements

This press release contains or incorporates by reference statements by Amentum Holdings, Inc. (the “Company”) that relate to future events and expectations and, as such, constitute “forward-looking statements” as that term is defined in the Private Securities Litigation Reform Act of 1995 and other federal securities laws. These forward-looking statements may be characterized by terminology such as “believe,” “project,” “expect,” “anticipate,” “estimate,” “forecast,” “outlook,” “target,” “endeavor,” “seek,” “predict,” “intend,” “strategy,” “plan,” “may,” “could,” “should,” “will,” “would,” “will be,” “will continue,” “will likely result,” or the negative thereof or variations thereon or similar terminology generally intended to identify forward-looking statements. All statements, other than historical facts, including, but not limited to, statements regarding the anticipated work and revenue under the awarded contract, and the Company’s objectives, expectations and intentions, applicable legal, economic and regulatory conditions, and any assumptions underlying any of the foregoing, are forward-looking statements.

A number of important factors could cause actual results to differ materially from those contained in or implied by these forward-looking statements, including those factors discussed in our filings with the Securities and Exchange Commission (SEC), including, among others: the occurrence of an accident or safety incident; the ability of the Company to control costs, meet performance requirements or contractual schedules; and other factors set forth under Item 1A, Risk Factors in our Annual Report on Form 10-K for the fiscal year ended September 27, 2024, which can be found at the SEC’s website at www.sec.gov or the Investor Relations portion of our website at www.amentum.com. Any forward-looking statement speaks only as of the date on which it is made, and the Company assumes no obligation to update or revise such statement, whether as a result of new information, future events or otherwise, except as required by applicable law.