Denison Announces Filing of Annual Report on Form 40-F

Press Release

TORONTO, March 30, 2026  – Denison Mines Corp. (“Denison” or the “Company”) (TSX: DML) (NYSE American: DNN) is pleased to announce that it has filed its 2025 Annual Report on Form 40-F with the U.S. Securities and Exchange Commission (“SEC”).  Denison’s Form 40-F includes its annual information form, management discussion and analysis, and audited financial statements for the year ended December 31, 2025.  The Form 40-F will be available on Denison’s website at www.denisonmines.com and on the SEC’s website at www.sec.gov/edgar. View PDF version

Denison’s annual information form has also been filed with Canadian regulatory authorities and will be available on Denison’s website at www.denisonmines.com and under the Company’s profile on SEDAR+ at www.sedarplus.ca.

Holders of Denison’s securities may receive a free printed copy of the Company’s most recent Annual Report on Form 40-F, including the audited financial statements, by sending an email request to info@denisonmines.com or by writing to Denison Mines Corp., 1100 – 40 University Avenue, Toronto, Ontario, Canada M5J 1T1.

About Denison

Denison is a leading uranium mining, development, and exploration company with interests focused in the Athabasca Basin region of northern Saskatchewan, Canada. Denison has an effective 95% interest in its flagship Wheeler River Uranium Project, which is the largest undeveloped uranium project in the infrastructure rich eastern portion of the Athabasca Basin region of northern Saskatchewan. In mid-2023, the Phoenix feasibility study was completed for the Phoenix deposit as an ISR mining operation, and an update to the previously prepared 2018 Pre-Feasibility Study (“PFS”) was completed for Wheeler River’s Gryphon deposit as a conventional underground mining operation. Based on the respective studies, both deposits have the potential to be competitive with the lowest cost uranium mining operations in the world. Permitting efforts for Phoenix commenced in 2019 and the required permits have been obtained to commence construction – including the July 2025 approval of the project’s Environmental Assessment (“EA”) by the Province of Saskatchewan and the February 2026 federal approval of the EA and issuance of the Construction Licence.

Denison’s interests in Saskatchewan also include a 22.5% ownership interest in the McClean Lake Joint Venture (“MLJV”), which restarted mining with SABRE in 2025) and the McClean Lake uranium mill (currently utilizing a portion of its licensed capacity to process the ore from the Cigar Lake mine under a toll milling agreement), plus a 25.17% interest in the Midwest Main and Midwest A deposits held by the Midwest Joint Venture (“MWJV”), and a 70.55% interest in the Tthe Heldeth Túé (“THT”) and Huskie deposits on the Waterbury Lake Property. The Midwest Main, Midwest A, THT and Huskie deposits are located within 20 kilometres of the McClean Lake mill. Taken together, the Company has direct ownership interests in properties covering ~457,000 hectares in the Athabasca Basin region.

Additionally, through its 50% ownership of JCU (Canada) Exploration Company, Limited (‘JCU’), Denison holds interests in various uranium project joint ventures in Canada, including the Millennium project (JCU, 30.099%), the Kiggavik project (JCU, 33.8118) and Christie Lake (JCU, 34.4508%).

In 2024, Denison celebrated its 70th year in uranium mining, exploration, and development, which began in 1954 with Denison’s first acquisition of mining claims in the Elliot Lake region of northern Ontario.

For more information, please contact: David Cates, (416) 979-1991 ext. 362 ,President and Chief Executive Officer; Geoff Smith, (416) 979-1991 ext. 358, Vice President Corporate Development & Commercial; Follow Denison on Twitter @DenisonMinesCo

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