Mr. David Cates reports

DENISON REPORTS FINANCIAL AND OPERATIONAL RESULTS FOR Q1 2023

Denison Mines Corp. today filed its condensed consolidated financial statements and management's discussion and analysis (MD&A) for the quarter ended March 31, 2023. Both documents will be available on the company's website, SEDAR and EDGAR. The highlights provided herein 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 (as is always the case for news releases posted under Canadian ticker symbols on Stockwatch).

David Cates, president and chief executive officer of Denison, commented: "Our Q1 2023 operational highlights showcase the multiple facets that make up our dynamic company. During the quarter at our flagship Wheeler River project, we progressed our efforts on the Phoenix deposit feasibility study, incorporating results from the highly successful leaching and neutralization phases of the feasibility field test completed in late 2022. With the FS nearing completion, and the environmental assessment for Phoenix progressing in parallel to our technical derisking efforts over the last several years, Phoenix remains squarely positioned to become the next new uranium mine in the eastern portion of the Athabasca basin region.

"We also reported notable news from other assets in our vast project portfolio -- including the discovery of high-grade uranium mineralization at the Moon Lake South exploration project and positive results from the completion of an internal concept study for the use of the in-situ recovery mining method at Denison's 25.17-per-cent-owned Midwest development project. The discovery at Moon Lake South is in the very early stages and illustrates the untapped potential of our large exploration property portfolio. Moon Lake South is a particularly exciting property, given that it is nearly surrounded by Denison controlled exploration properties and is adjacent to our flagship Wheeler River property. At Midwest, we are collaborating with our long-time joint venture partner Orano Canada Inc., to take steps that could see Midwest emerge as another meaningful source of low-cost future production for Denison. Based on the positive results of the concept study, the Midwest joint venture has approved a program and budget for 2023 that will support the further derisking of the application of the ISR mining method at Midwest, and which may result in the completion of a preliminary economic assessment.

"With truly meaningful developments ahead on multiple Denison projects and the uranium market benefiting from a sustained stream of positive developments increasing projections of global demand for nuclear power, Denison is well positioned to offer investors unique leverage to the uranium market from our multistage/multiasset portfolio of high-grade Athabasca basin projects."

Highlights

• Completed an internal concept study examining the application of the ISR mining method at Midwest.

The company completed a concept study examining the potential application of the ISR mining method at Midwest. The concept study was prepared by Denison during 2022 and formally issued to the Midwest joint venture in early 2023. Based on the positive results of the concept study, the MWJV has provided Denison with approval to complete additional ISR-related work for Midwest in 2023.

Evaluation activities planned for Midwest during 2023 include the collection of deposit-specific information and the completion of select preliminary engineering studies to support the further evaluation and derisking of the key criteria required to further assess the potential application of the ISR mining method, which may result in the preparation of a PEA to support the development, if warranted, of future field tests.

• Discovered high-grade uranium mineralization at Moon Lake South.

In April, 2023, Denison reported that drill hole MS-23-10A intersected 1.38 per cent eU3O8 over 8.7 metres (0.05 per cent eU3O8 cut-off), including a subinterval grading 2.88 per cent eU3O8 over 3.1 metres, intersected approximately 30 metres above the unconformity in the Athabasca sandstone, as part of the recently completed winter exploration program at the Moon Lake South property. Uranium mineralization was encountered in four of the six drill holes completed during the 2023 winter exploration program, which was designed to evaluate the strike length of low-grade mineralized occurrences identified in the 2021 and 2016 drill programs.

• Feasibility study for Wheeler River Phoenix deposit on track for completion by mid-2023.

Feasibility level engineering design, well field production modelling and cost estimation for the application of ISR mining for the high-grade Phoenix uranium deposit at Wheeler River progressed during the first quarter of 2023, and is currently on track to support the announcement of the results from the FS by mid-2023.

• Released 2022 ESG (environmental, social and governance) report, highlighting progress on environmental, social and governance initiatives.

In April, 2023, Denison released its 2022 ESG report, which provides information on the company's environmental, social and governance (ESG) initiatives and demonstrates its continuing commitment to sustainability and transparency. Denison's 2022 ESG report focuses on key ESG topics including the company's objective to maintain excellence in corporate governance practices, best-in-class engagement with communities potentially impacted by its activities, diversity in the company's work force, and robust assessments of the environment and biodiversity in the regions within which it operates.

About Denison Mines Corp.

Denison is a uranium exploration and development company with interests focused in the Athabasca basin region of Northern Saskatchewan, Canada. The company has an effective 95-per-cent 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. Denison's interests in Saskatchewan also include a 22.5-per-cent ownership interest in the McClean Lake joint venture, which includes several uranium deposits and the McClean Lake uranium mill that is contracted to process the ore from the Cigar Lake mine under a toll milling agreement, plus a 25.17-per-cent interest in the Midwest Main and Midwest A deposits, and a 67.41-per-cent interest in the Tthe Heldeth Tue (THT, formerly J zone) and Huskie deposits on the Waterbury Lake property. The Midwest Main, Midwest A, THT and Huskie deposits are each located within 20 kilometres of the McClean Lake mill.

Through its 50-per-cent ownership of JCU, Denison holds additional interests in various uranium project joint ventures in Canada, including the Millennium project (JCU: 30.099 per cent), the Kiggavik project (JCU: 33.8118 per cent) and Christie Lake (JCU: 34.4508 per cent). Denison's exploration portfolio includes further interests in properties covering approximately 300,000 hectares in the Athabasca basin region.

Denison is also engaged in postclosure mine care and maintenance services through its Closed Mines group, which manages Denison's reclaimed mine sites in the Elliot Lake region and provides related services to certain third party projects.

Technical disclosure and qualified person

The technical information contained in this press release has been reviewed and approved by Chad Sorba, PGeo, Denison's director, technical services, and Andy Yackulic, PGeo, Denison's director, exploration, who are both qualified persons in accordance with the requirements of National Instrument 43-101.

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