Denison CEO Highlights Phoenix Post-Feasibility Study Progress and Company Reports Financial and Operational Results for Q2’2024

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Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

PRESS RELEASE

Denison CEO Highlights Phoenix Post-Feasibility Study Progress and

Company Reports Financial and Operational Results for Q2’2024

Toronto, ON – August 8, 2024. 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 three and six months ended June 30, 2024. Both docum ents will be available on the Company’s website at

www.denisonmines.com, SEDAR+ (at www.sedarplus.ca) and EDGAR (at www.sec.gov/edgar.shtml). The highlights

provided below are derived from these documents and sho uld be read in conjunction with them. All amounts in this

release are in Canadian dollars unless otherwise stated.

David Cates, President and CEO of Denison commented, “Following the completion of our Phoenix Feasibility Study

(‘FS’) in June 2023, we embarked on an ambitious 2-year plan to advance towards a final investment decision. At the

end of the second quarter of 2024, we have completed 12-months of post-FS project work and have already achieved

completion of over 30% total engineering. Our rapid engineering progress is possible because we have built off of the

systematic and rigorous technical evaluation and de-risking wo rk that was incorporated into the FS. The FS already

reflects the wave of significant cost inflation experi enced in the mining sector from 2021 to 2023 and robust project

designs that incorporated the learnings from the envi ronmental assessment proces s as described in our draft

Environmental Impact Statement (‘EIS’) submitted in 2022. Engineering and ongoing long-lead procurement efforts

continue to accelerate in accordance with our project plans and guidance targeting first production by 2027 / 2028.

In parallel, we have obtained support for the project from Indigenous and non-Indigenous interested parties – reaching

impact-benefit type agreements, supporting the advancement and operation of the Wheeler River project, with each of

English River First Nation, Kineepik Métis Local #9, the Village of Pinehouse, and a gr oup of interested northern

municipalities (the Northern Village of Beauval, the Northern V illage of Île-à-la Crosse, the Northern Hamlet of Jans

Bay, and the Northern Hamlet of Cole Ba y). Additionally, we have made signi ficant progress towards the finalization

of our EIS, project permitting, and licensing. Based on feedback received to date, we are optimistic that the EIS review

process is nearing completion.

Ending Q2 with no debt on the balance sheet and a combinat ion of working capital and investments valued at nearly

95% of Denison’s share of the Phoenix FS initial capex means that our Compan y is very well funded to continue to

execute on our project development plans and to deliver a new source of Canadian uranium supply to the market at a

time when demand is increasing and securing sustainable a nd geopolitically stable supply is expected to be a priority

for future utility customers.

Beyond Wheeler River, Denison continues to demonstrate its industry leadership in the assessment of the application

of the low-cost ISR mining method to the high-grade uranium deposits of the Athabasca Basin. In 2024, we are carrying

out field studies and evaluation program s at both the Tthe Heldeth Túé (‘THT’) and Midwest Main deposits. Working

together with Orano Group, a global leader in the nuclear f uel cycle, we recently completed an inaugural field test of

ISR mining at the Midwest Main deposit, providing import ant preliminary validation that the deposit possesses the

characteristics necessary for an ISR operation and efforts are now focused on the completion of a Preliminary Economic

Assessment (‘PEA’) during the balance of the year.”

Q2 2024 MD&A Highlights

 Completion of Inaugural ISR Field Test Program at Midwest

In June 2024, Denison and Orano Canada Inc. (‘Orano Canada’) announced the completion of an In-Situ Recovery

(‘ISR’) field test program at the Company’s 25.17% ow ned Midwest Uranium Project (‘Midwest’). The program

involved drilling ten small diameter boreholes within the Midwest Main deposit primarily undertaken to evaluate site-

specific conditions for ISR mining. A series of tests were successfully performed on each borehole, creating an

extensive database of geologi cal, hydrogeological, geotechnical, and me tallurgical data and validating certain key

assumptions in the previously completed internal conc eptual mining study (the ‘C oncept Study’) evaluating the

potential use of ISR mining at Midwest (see Press Release dated April 12, 2023).

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Denison carried out the program in collaboration with Orano Canada, as operator a nd owner of 74.83% of the

Midwest Joint Venture (‘MWJV’). Highlights from the program include:

 Confirmation of Hydraulic Conductivity: Pump and injection tests validated hydraulic connectivity in the test

wells within the mineralized zone and achieved hydraulic conductivity values (a measure of permeability)

consistent with the Concept Study. Suffi cient permeability within the mineraliz ed zone is a key criterion for the

successful deployment of the ISR mining method.

 Demonstrated the Effectiveness of Permeability Enhancement: One method of permeability enhancement

was successfully deployed within two wells, demonstrati ng the suitability of the me thod to the Midwest Main

deposit. Efficiency of permeability enhancement was veri fied by comparison of pre- and post-permeability

enhancement hydraulic testing.

 Metallurgical Samples Defined and Collected for Leaching Characteristics : Core samples representative

of the Midwest Main deposit were collected during the pr ogram for use in future meta llurgical tests to assess

leaching characteristics.

 Signing of Wheeler River Benefit Agreements with Kineepik Métis Local #9 and the Village of Pinehouse Lake

In early July 2024, Denison announced the signing of a Mutual Benefits Agreement (‘MBA’) with Kineepik Métis Local

#9 (‘KML’), and a Community Benefit Agreement (‘CBA’) with the northern Village of Pinehouse Lake (the ‘Village’),

in support of the development and operation of Denison’s 95% owned Wheeler River Project.

The MBA acknowledges that the project is located within KML’s Land and Occupancy Area in northern Saskatchewan

and provides KML’s consent and support to advance the project. Additionally, the MBA recognizes that the

development and operation of the project can support KML in advanci ng its social and economic development

aspirations, while mitigating the impacts on the local environment and KML members. Key commitments of the MBA

include providing KML and its Métis members an important role in environmental monitoring and commits to the

sharing of benefits from the successful operation of the project – includi ng benefits from community investment,

business opportunities, employment and training opportunities, and financial compensation.

The CBA acknowledges that the Village is the closest resi dential community to the project by road, which relies on

much of the same regional infrastructure that Denison will rely on as it advances the project. The Village has provided

its consent and support for the project, while Denison, on behalf of the Wheeler River Joint Venture, is committed to

help the Village develop its own capacity to take advant age of economic and other devel opment opportunities in

connection with the advancement and operation of the project.

 Appointment of New Board Chair

In May 2024, following the results of the Annual General Meeting of Shareholders (‘AGM’) held in Toronto, Denison

announced the appointment of Ms. Jennifer Traub as the Company’s new Board Chair. The former Board Chair, Mr.

Ron Hochstein, did not stand for re-election at the AGM. Ms. Traub, who joined the Denison Board in 2021, is a

partner in the Securities Group, and Co-Chair of the Mining Group, at Cassels Brock & Blackwell LLP, and has been

recognized as a legal leader in the Canadian resource sector.

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 To ronto 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 proj ect in the infrastructure rich eastern portion of the

Athabasca Basin region of northern Sa skatchewan. In mid-2023, the Phoeni x FS 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 c onventional underground mini ng operation. Based on the

respective studies, both deposits have t he 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 Enviro nmental Impact Study (‘EIS’) submitted for regulatory and

public review in October 2022.

Denison’s interests in Saskatchewan also include a 22.5% ownership interest in the McClean Lake Joint Venture

(‘MLJV’), which includes unmined uranium deposits (planned for extraction via the MLJV’s SABRE mining method

starting in 2025) and the McClean Lake uranium mill (currently utilizing a portion of its licensed capacity to process the

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ore from the Cigar Lake mine under a toll milling agreement) , plus a 25.17% interest in the Midwest Joint Venture

(‘MWJV’)’s Midwest Main and Midwest A deposits, and a 69.44% interest in the Tthe Heldeth Túé (‘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 ~384,000 hectares in the Athabasca Basin region.

Additionally, through its 50% ownership of JCU (Canada) Explorat ion Company, Limited (‘JCU’), Denison holds

interests in various uranium project joint ventures in Ca nada, including the Millennium project (JCU, 30.099%), the

Kiggavik project (JCU, 33.8118%) and Christie Lake (JCU, 34.4508%).

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, and Andy Yackulic, P.Geo., Denison’s Vice

President Exploration, who are both Qualified Persons in accordance with the requirements of NI 43-101.

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

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Certain information contained in this pre ss release constitutes ‘forward-looking info rmation’, within the meaning of the applic able

United States and Canadian legislation conc erning the business, operations and financ ial performance and condition of Denison.

Generally, these forward-looking statements c an be identified by the use of forward-look ing 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: projections with respect to exploration,

development and expansion plans and objectives, including the scope, objectives and in terpretations of FS, PFS and the Wheeler

River technical de-risking process for the proposed ISR operation for the Phoenix depos it; expectations with respect to the EA, EIS

and licensing and permitting for proposed operati ons at Wheeler River; ex pectations regarding the rest art of mining operations at

McClean Lake; expectations regar ding the assessment of the amenability of IS R for THT and Midwest deposits; expectations

regarding the performance of the uranium market and global sentiment regarding nucl ear energy; expectations regarding Denison’s

joint venture ownership interests; and expectations regarding th e objectives and continuity of its agreements with third partie s.

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 c ause the actual results, level of activi ty,

performance or achievements of Denison to be materially different from those expre ssed or implied by such forward-looking

statements. For example, the results and underlying assumptions and interpretations of the FS and PFS may not be maintained after

further testing or be representative of actual conditions within the applicable deposits. In addition, Denison may decide or o therwise

be required to discontinue testing, evaluati on, engineering, and development work if it is unable to maintain or otherwise secu re the

necessary approvals or resources (such as testing facilities, capital funding, etc.). 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 fo rward-looking information. For a discussion in respect of risks and other

factors that could influence forward-looking events, please refer to the factors discu ssed in the Company’s Annual Information Form

dated March 28, 2024 under the heading ‘Risk Factors’. These factors are not, and should not be, construed as being exhaustive.

Accordingly, readers should not place undue re liance on forward-looking statements. The forward-looking information contained i n

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 rel ease to conform such information to actual results or to change s in

Denison's expectations except as otherwise required by applicable legislation.