Denison Mines Corp. ("Denison" or the "Company") (TSX: DML) (NYSE American: DNN) today filed its Condensed Consolidated Financial Statements and Management's Discussion & Analysis ('MD&A') for the quarter ended March 31, 2026. Both documents will be available on the Company's website (at www.denisonmines.com), SEDAR+ (at www.sedarplus.ca) and EDGAR (at www.sec.gov/edgar). The highlights provided below are derived from these documents and should be read in conjunction with them. All amounts in this release are in Canadian dollars unless otherwise stated. View PDF Version

David Cates, President and CEO of Denison commented, "In February, the Phoenix In-Situ Recovery ("ISR") uranium mine ("Phoenix") became the first large-scale Canadian uranium mining project in over 20 years to receive all regulatory approvals required to commence construction. Shortly after achieving this landmark permitting accomplishment, the Company made its final investment decision ("FID") for Phoenix construction and, by the end of the first quarter, our Denison-Wood integrated project management team mobilized to the Wheeler River property and began executing schedule-critical site preparation and early works construction activities.

In less than two months of on-site activity, our dedicated teams have completed (i) tree clearing activities across the primary mine site area, (ii) installation of construction management facilities, (iii) construction of our on-site helipad, (iv) civil works for the concrete batch plant pad, and (v) commencement of aggregate production at a nearby quarry. Civil activities continue to advance on site, including those necessary to establish the future airstrip. Taken together, we are on track to ramp up construction staffing and activities to complete early works and commence full-scale construction by the end of the second quarter, which aligns with our target to achieve first uranium production in mid-2028. We are, however, closely monitoring the widespread flooding that is impacting a portion of the road network in northern Saskatchewan. While our personnel are able to access the Phoenix site via helicopter, our ability to mobilize additional heavy equipment and certain supplies to site as planned may be impacted if the flooding persists and/or key infrastructure remains impacted. We recognize the significant efforts of the Province of Saskatchewan to rapidly respond to this unprecedented situation and are hopeful that conditions will improve in the coming days.

At our 22.5%-owned McClean Lake operation, mining activities at the McClean North SABRE mine were minimal in the first quarter, with work focused on the completion of resource confirmation drilling in advance of the planned resumption of active mining later in the second quarter. 

Denison's unique combination of physical uranium holdings, active mine production from McClean Lake, and large-scale expected future mine production from the Phoenix and Gryphon deposits has resonated positively with some of the world's largest nuclear power utilities. This is reflected by our continued success in growing our uranium sales book â?? which now includes contracted sales commitments for nearly 8 million pounds of U3O8 plus advanced negotiations for a further 8 million pounds of U3O8. Notably, our customers include leading North American nuclear power utilities collectively responsible for over 50 reactors.

In the first quarter, we entered near-term sales commitments with an average realized price over US$99/lb U3O8 for deliveries within a year. These sales are part of our Phoenix project financing efforts stemming from our physical uranium purchase from 2021, and demonstrate how our disciplined long-term strategy has facilitated significant participation in a rising uranium price environment. While the large majority of our commercial activity is focused on market-related pricing, we have also recently observed base-escalated pricing above levels reported in industry price publications, including prices on a present value basis in excess of US$100/lb U3O8 We believe this and other positive market signals continue to point to robust uranium market fundamentals, which align well with Denison's unique position as one of the few uranium suppliers globally that is on track to bring a sizeable new source of production to market before the end of the decade."

Highlights

2026 Annual Shareholders Meeting

Denison is also pleased to report the passing of all items of business presented to shareholders at the Company's annual and special shareholders meeting held in Toronto today (the "Meeting"), as disclosed in the management information circular dated March 30, 2026. Detailed results of the vote by proxy for the election of directors are set out below.

The Company has provided more details on the results of all matters considered at the Meeting in its Report of Voting Results which has been filed under its profile on SEDAR+ at www.sedarplus.ca and on EDGAR at www.sec.gov/edgar.

About Denison

Denison Mines Corp. was formed under the laws of Ontario and is a reporting issuer in all Canadian provinces and territories. Denison's common shares are listed on the Toronto Stock Exchange (the "TSX") under the symbol 'DML' and on the NYSE American exchange under the symbol 'DNN'.

Denison is a uranium mining, exploration and development company with interests focused in the Athabasca Basin region of northern Saskatchewan, Canada. The Company 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 FS was completed for the Phoenix ISR mining operation, and an update to the 2018 Pre-Feasibility Study ("2018 PFS") was completed for the Gryphon deposit as a conventional underground mining operation (the "Gryphon Update"). 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 â?? including the July 2025 approval of the project's EA by the Province of Saskatchewan and the February 2026 federal approval of the EA and issuance of the Construction Licence. This milestone supported the FID and the subsequent commencement of early works activities at the Phoenix mine. Denison's interests in Saskatchewan also include a 22.5% ownership interest in the 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 Tàºé ("THT") and Huskie deposits on the Waterbury Lake Property ("Waterbury"). 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 further 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.

Technical Disclosure and Qualified Person

The technical information contained in this press release has been reviewed and approved by Chad Sorba, P.Geo., Denison's Vice President Technical Services & Project Evaluation, who is a Qualified Persons in accordance with the requirements of NI 43-101.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Certain information contained in this press release constitutes 'forward-looking information', within the meaning of the applicable United States and Canadian legislation concerning the business, operations, and financial performance and condition of Denison. Generally, these forward-looking statements can be identified by the use of forward-looking terminology such as 'plans', 'expects', 'budget', 'scheduled', 'estimates', 'forecasts', 'intends', 'anticipates', or 'believes', or the negatives and/or variations of such words and phrases, or state that certain actions, events or results 'may', 'could', 'would', 'might' or 'will be taken', 'occur', 'be achieved' or 'has the potential to'.

In particular, this press release contains forward-looking information pertaining to the following: the results of, and estimates and assumptions within, the Phoenix FS and the Gryphon PFS Update, including the estimates of Denison's mineral reserves and mineral resources, and statements regarding anticipated budgets, fees, expenditures and timelines; Denison's outlook, plans and objectives for 2026 and beyond; exploration, development and construction programs, plans and objectives, including expectations with respect to early works and commencement of construction at Phoenix; statements regarding impacts of flooding including its impacts on road networks in northern Saskatchewan; statements regarding Denison's EA and Construction Licence approvals and other expectations with respect to Denison's project licensing and permitting; expectations regarding uranium mining on the McClean Lake property, including anticipated timing and budgets; Denison's land position; expectations regarding Denison's joint venture ownership interests and the continuity of its agreements with its partners; expectations regarding agreements with third parties, including Foremost, Cosa, and Skyharbour; and Denison's plans with respect to its commercial activities, including its physical uranium holdings and other uranium sales transactions and the expected benefits thereof. Statements relating to 'mineral reserves' or 'mineral resources' are deemed to be forward-looking information, as they involve the implied assessment, based on certain estimates and assumptions that the mineral reserves and mineral resources described can be profitably produced in the future.

Forward looking statements are based on the opinions and estimates of management as of the date such statements are made, and they are subject to known and unknown risks, uncertainties and other factors that may cause the actual results, level of activity, performance or achievements of Denison to be materially different from those expressed or implied by such forward-looking statements. For example, the results of the Denison's studies, including the Phoenix FS, and field work, may not be maintained after further testing or be representative of actual mining plans for the Phoenix deposit after further design and studies are completed. In addition, Denison may decide or otherwise be required to discontinue early works and/or construction at Phoenix or other exploration, testing, evaluation and development work at Wheeler River or other projects if it is unable to maintain or otherwise secure the necessary resources (such as testing facilities, capital funding, regulatory approvals, etc.) or operations are otherwise affected by regulatory restrictions or requirements.

Denison believes that the expectations reflected in this forward-looking information are reasonable, but no assurance can be given that these expectations will prove to be accurate, and results may differ materially from those anticipated in this forward-looking information. For a discussion in respect of risks and other factors that could influence forward-looking events, please refer to the factors discussed under the heading 'Risk Factors' in the Company's most recent Annual Information Form. These factors are not, and should not be construed as being, exhaustive. Accordingly, readers should not place undue reliance on forward-looking statements. The forward-looking information contained in this press release is expressly qualified by this cautionary statement. Any forward-looking information and the assumptions made with respect thereto speaks only as of the date of this press release. Denison does not undertake any obligation to publicly update or revise any forward-looking information after the date of this press release to conform such information to actual results or to changes in Denison's expectations except as otherwise required by applicable legislation.

SOURCE Denison Mines Corp.

SOURCE: Denison Mines Corp.

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

COMTEX_479023705/2197/2026-05-12T20:16:00