Mr. David Cates reports

DENISON REPORTS FINANCIAL AND OPERATIONAL RESULTS FOR Q2 2023

Denison Mines Corp. has filed its condensed consolidated financial statements, and management's discussion and analysis (MD&A) for the quarter ended June 30, 2023. Both documents are, or will be, available on the company's website, SEDAR+ and EDGAR. The highlights provided below are derived from these documents and should be read in conjunction with them.

David Cates, president and chief executive officer of Denison, commented: "During the second quarter, Denison achieved a further notable milestone associated with the advancement of our flagship Wheeler River project with the completion of: (i) a highly successful feasibility study (FS) evaluating the use of in situ recovery (ISR) mining for the high-grade Phoenix uranium deposit; and (ii) a positive cost update to the prefeasibility study (PFS) for the underground mine planned for the Gryphon uranium deposit.

"As outlined in the Phoenix FS, Denison has successfully completed several years of technical derisking, which has cemented Phoenix's position as one of the lowest-cost uranium development projects in the world. Notably, the economics of Phoenix as an ISR mining operation remain exceptionally robust, despite industry-wide cost inflation, while most contemporary uranium development projects have not yet been tested against current cost inflation. The recent results of the Phoenix FS and Gryphon update illustrate Denison's unique potential to become a meaningful uranium producer with multiple low-cost development assets.

"Global support for the role of nuclear power in the clean energy transition continues to grow and uranium buyers are increasingly prioritizing geopolitical stability. Denison is well funded, with over $235-million in working capital and investments at the end of the second quarter, and focused on advancing Phoenix to a final investment decision in anticipation of building a much-needed new source of Canadian uranium production."

Highlights

Feasibility study for Wheeler River Phoenix deposit yields significant increase in economic results

In June, 2023, Denison released the results of the Phoenix FS completed for ISR mining of Phoenix. The Phoenix FS demonstrates robust economics, including:

• Base case pretax net present value (NPV) at an 8-per-cent discount of $2.34-billion (100-per-cent ownership basis), representing an 150-per-cent increase in the base case pretax NPV at an 8-per-cent discount for Phoenix from the 2018 prefeasibility study.
• Very robust base case pretax internal rate of return (IRR) of 105.9 per cent.
• Adjusted base case after-tax NPV at an 8-per-cent discount of $1.56-billion (100-per-cent basis) and IRR of 90 per cent -- with Denison's effective 95-per-cent interest in the project equating to an adjusted base case after-tax NPV at an 8-per-cent discount of $1.48-billion.
• Base case pretax and after-tax (adjusted) payback period of 10 months -- equating to a reduction of 11 months for the pretax payback period from the 2018 PFS.
• Optimized production profile, based on ISR mine planning efforts evaluating production potential for individual well patterns -- resulting in an increase to the planned rate of production by approximately 43 per cent during the first five years of operations.
• Estimated preproduction capital costs of under $420-million (100-per-cent basis), yielding an impressive base case after-tax (adjusted) NPV to initial capital cost ratio in excess of 3.7 to 1.
• Robust economics that easily absorb cost inflation and design changes impacting both operating and capital costs, confirming Phoenix's position with estimated cash operating and all-in costs expected to be amongst the lowest-cost uranium mines in the world.
• Phoenix FS plans aligned and costed to meet or exceed environmental criteria expected to be required by the continuing regulatory approval process.
• Updated mineral resource estimate, reflecting the results of 70 drill holes completed in support of ISR derisking and resource delineation activities, which has upgraded 30.9 million pounds U3O8 (triuranium octoxide) into measured mineral resources, and increased the average grade of the Zone A high-grade domain. This zone is now estimated to contain 56.3 million pounds U3O8 in measured and indicated mineral resources at an average grade of 46 per cent U3O8.
• Upgraded 3.4 million pounds U3O8 into proven mineral reserves, representing the equivalent of 85 per cent of production planned during the first calendar year of operations.

Completion of Phoenix ISR derisking and transition to engineering design

The Phoenix FS reflects independent third party validation of the selection of the ISR mining method for Phoenix, and builds on the findings from a comprehensive and rigorous multiyear technical derisking process, highlighted by the highly successful completion of the leaching and neutralization phases of the Phoenix feasibility field test (FFT) in late 2022. Through the technical derisking process, Denison has acquired extensive deposit-specific data and developed a robust ISR mine planning model that involved evaluation of the production potential for individual well patterns.

With technical derisking of the project substantially complete, front-end engineering design efforts to support the advancement of the planned Phoenix operation are already significantly progressed, and the company is on schedule to transition into detailed design efforts, consistent with the company's outlook for 2023, before the end of the year.

Cost update to the 2018 PFS for Wheeler River Gryphon deposit confirms the project remains to be positioned amongst the lowest-cost uranium mines in the world

The scope of the Gryphon update was targeted at the review and update of capital and operating costs. Mining and processing plans remain largely unchanged from the 2018 PFS, aside from minor scheduling and construction sequencing optimizations. The key points include:

• Base case pretax NPV at an 8-per-cent discount of $1.43-billion (100-per-cent basis) is a 148-per-cent increase in the base case pretax NPV (8 per cent) for Gryphon from the 2018 PFS.
• Strong base case pretax IRR of 41.4 per cent.
• Base case after-tax NPV (8 per cent) of $864.2-million (100-per-cent basis) and IRR of 37.6 per cent -- with Denison's effective 95-per-cent interest in the project equating to a base case after-tax NPV (8 per cent) of $821-million.
• Base case pretax payback period of 20 months and base case after-tax payback period of 22 months -- equating to a reduction of 17 months for the pretax payback period from the 2018 PFS.

Importantly, Gryphon remains a highly valuable project that provides Denison with an additional source of low-cost potential production to deploy significant free cash flows expected from Phoenix.

About Denison Mines Corp.

Denison Mines was formed under the laws of Ontario, and is a reporting issuer in all Canadian provinces and territories.

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. In mid-2023, a feasibility study was completed for Wheeler River's Phoenix deposit as an ISR mining operation, and an update to the previously prepared 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 the planned Phoenix ISR operation commenced in 2019 and have advanced significantly, with licensing in progress, and a draft environmental impact statement (EIS) submitted for regulator and public review October, 2022.

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 Japan (Canada) Exploration Company Ltd. (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 285,000 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.

Further details of the Phoenix FS and Gryphon update are provided in Denison's press release of June 26, 2023. The results of the Phoenix FS and Gryphon update are also detailed in a technical report entitled "NI 43-101 Technical Report on the Wheeler River Project Athabasca Basin, Saskatchewan, Canada," with an effective date of June 23, 2023, and dated Aug. 8, 2023. The technical report is, or will be, available on the company's website, on SEDAR+ and on EDGAR.

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