Denison Mines : Investor Update - September 2021

Uranium Development & Exploration

The Athabasca Basin, Northern Saskatchewan

September 2021 | Corporate Update

Cautionary Statements & References

This presentation and the information contained herein is designed to help you understand management's current views, and may not be appropriate for other purposes. This presentation contains information relating to the uranium market, third party and provincial infrastructure, and the plans and availability thereof, derived from third-party publications and reports which Denison believes are reliable but have not been independently verified by the Company.

Certain information contained in this presentation constitutes "forward-looking information", within the meaning of the United States Private Securities Litigation Reform Act of 1995 and similar Canadian legislation concerning the business, operations and financial performance and condition of Denison. Generally, these forward-lookingstatements can be identified by the use of forward-lookingterminology 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 presentation contains forward-lookinginformation pertaining to the results of, and estimates, assumptions and projections provided in, the Wheeler PFS and the Waterbury PEA, including future development methods and plans, market prices, costs and capital expenditures; assumptions regarding Denison's ability to obtain all necessary regulatory approvals to commence development at Wheeler; Denison's percentage interest in its projects and its agreements with its joint venture partners; and the availability of services to be provided by third parties. Statements relating to "mineral resources" are deemed to be forward-lookinginformation, as they involve the implied assessment, based on certain estimates and assumptions that the 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. Denison faces certain risks, including the current and potential impacts of the COVID-19pandemic, use of mining methods which are novel and untested in the Athabasca basin, the inability to permit or develop its projects as currently planned, the inability to secure sufficient financing to pursue its business objectives, the unpredictability of market prices, events that could materially increase costs, changes in the regulatory environment governing the project lands, and unanticipated claims against title and rights to the project. Denison believes that the expectations reflected in this forward-lookinginformation are reasonable but there can be no assurance that such statements will prove to be accurate and 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-lookingevents, please refer to the "Risk Factors" in Denison's Annual Information Form dated March 13, 2020 available under its profile at www.sedar.com and its Form 40-Favailable at www.sec.gov/edgar.shtml. These factors are not, and should not be construed as being exhaustive.

Readers should not place undue reliance on forward-lookingstatements. The forward-looking information contained in this presentation is expressly qualified by this cautionary statement. Any forward-looking information and the assumptions made with respect thereto speaks only as of March 13, 2020. Denison does not undertake any obligation to publicly update or revise any forward-looking information after such date to conform such information to actual results or to changes in its expectations except as otherwise required by applicable legislation.

Cautionary Note to United States Investors Concerning Estimates of Mineral Resources and Mineral Reserves: This presentation may use terms such as "measured", "indicated" and/or "inferred" mineral resources and "proven" or "probable" mineral reserves, which are terms defined with reference to the guidelines set out in the Canadian Institute of Mining, Metallurgy and Petroleum ("CIM") CIM Definition Standards on Mineral Resources and Mineral Reserves ("CIM Standards"). The Company's descriptions of its projects may not be comparable to similar information made public by U.S. companies subject to the reporting and disclosure requirements under the United States federal securities laws and the rules and regulations thereunder.

Qualified Persons

The disclosure of a scientific or technical nature within this presentation, including the disclosure of mineral resources, mineral reserves, as well as the results of the Wheeler PFS and Waterbury PEA, was reviewed and approved by David Bronkhorst, P.Eng., who is a Qualified Person in accordance with the requirements of NI 43-101.

Technical Reports

• For further details regarding the Wheeler River project, please refer to the Company's press release dated September 24, 2018 and the technical report titled "Prefeasibility Study for the Wheeler River Uranium Project, Saskatchewan, Canada" with an effective date of September 24, 2018 ("Wheeler PFS").
• For further details regarding the Waterbury Lake project, please refer to the Company's press release dated November 17, 2020 and the technical report titled "Preliminary Economic Assessment for the Tthe Heldeth Túé (J Zone) Deposit, Waterbury Lake Property, Northern Saskatchewan, Canada" with an effective date of October 30, 2020 ("Waterbury PEA"). The PEA is a preliminary analysis of the potential viability of the Project's mineral resources, and should not be considered the same as a Pre-Feasibilityor Feasibility Study, as various factors are preliminary in nature. There is no certainty that the results from the PEA will be realized. Mineral resources are not mineral reserves and do not have demonstrated economic viability. Scheduled tonnes and grade do not represent an estimate of mineral reserves.

For a description of the data verification, assay procedures and the quality assurance program and quality control measures applied by Denison, please see Denison's Annual Information Form dated March 13, 2020. Copies of the foregoing are available on Denison's website and under its profile on SEDAR at www.sedar.com and on EDGAR at www.sec.gov/edgar.shtml.

2

The Uranium Investment Thesis:

Fundamentals are progressing towards a positive new uranium cycle

Annual Utility Uranium Requirements (1) (million pounds U3O8 - per UxC Q1'21)

250
200
150	Covered
	Demand
100
									Uncovered
										Demand
50
0									2030
2021	2022	2023	2024	2025	2026	2027	2028	2029	2031	2032	2033	2034	2035

Key Market Themes:

1. Demand story is positive - requirements now exceed pre-Fukushima levels & clean-energytransition movement has identified the critical role of nuclear in battle against climate change.
2. Significant curtailment decisions have been made by largest uranium producers - creating a significant primary production deficit.
3. Response to COVID-19 has put additional pressure on supply. Further curtailments have accelerated the drawdown of surplus inventories.
4. Long-termcontracts from the previous uranium cycle are coming to an end, with significant uncovered utility requirements emerging.
5. Given sustained low prices, project pipeline may be inadequate to deliver new production in time to replace mines that are dropping off
6. Investor interest in uranium market has increased, with investments in physical uranium gaining in popularity

NOTES: (1) Data in this slide has been derived from UxC's Uranium Market Outlook dated Q1 2021.

3

Diversified Athabasca Basin

Asset Base with Superior

Development Leverage

Strategic Asset Portfolio:

• 95% effective interest in Wheeler River project(1)
• • Largest undeveloped uranium project in the infrastructure rich eastern Athabasca Basin
  • Feasibility Study ("FS") and Environmental Assessment ("EA") in progress (2)(3)
• 22.5% interest in McClean Lake Uranium Mill
• • Operating mill with excess licensed capacity
• 66.90% interest in Waterbury Lake project
• • PEA(4) for Tthe Heldeth Túé("THT") deposit (formerly J Zone) highlights potential for future development portfolio
• Additional leverage to the uranium price
• • McClean Lake, Midwest, and Waterbury Lake all near McClean Lake mill
  • Interests in Millennium, Kiggavik and Christie Lake through 50% ownership of JCU(1)
• Strong balance sheet (as at June 30th, 2021)
• • ~CAD$107M (4) in cash & equity investments,
  • 2.3 million lbs U3O8 physical uranium

(commitments for 2.5 million lbs U3O8 at US$29.61/lb)(5)

4

NOTES: See Denison news releases dated (1) August 3, 2021; (2) November 9, 2021;

(3) September 22, 2021; (4) August 5, 2021; and (5) April 1, 2021.

22.5% Denison owned McClean Lake uranium mill

Denison's Development Portfolio:

Multiple projects positioned amongst the lowest all-in cost assets of UxC's First Tier

Sample of Global Production Costs(1)(2)(3)
Planned and Producing Operations (with Mining Method)	"Third/Fourth Tier"

$50.00

8

"Second Tier"

O

$45.00

3

U

$40.00

- USD$/lb

$35.00

UxC's "First Tier"

$30.00

(includes projects with full costs sub ~US$33/lb U3O8)

US$24.93

US$22.82

Costs

$25.00

$20.00

Full

$15.00

/

US$8.90

-in

$10.00

All

$5.00

ISR

ISR

ISR

ISR

UG

ISR

UG

UG

UG

UG

ISR

ISR

UG

ISR

OP

$0.00

Denison/Canada

Canada

Kazakhstan

Australia

United States

Africa

NOTES: (1) Chart data, including all-in costs and UxC's categorization of production cost "tiers", have been derived from UxC's estimates of Worldwide	5
Production Costs from the Uranium Production Cost Study dated August 2021; (2) For Phoenix and Gryphon, refer to the Wheeler River Technical Report titled
"Pre-feasibility Study Report for the Wheeler River Uranium Project, Saskatchewan, Canada" dated September 24, 2018. (3) for Tthe Heldeth Túé(Waterbury),
refer to the Waterbury Lake Technical Report titled "Preliminary Economic Assessment for the Tthe Heldeth Túé (J Zone) Deposit, Waterbury Lake Property,
Northern Saskatchewan, Canada" dated October 30, 2020.