Denison Announces Filing of Technical Report FOR Waterbury Lake Property

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

@DenisonMinesCo

PRESS RELEASE

DENISON ANNOUNCES FILING OF TECHNICAL REPORT

FOR WATERBURY LAKE PROPERTY

Toronto, ON – December 21, 2018 Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:

NYSE MKT) today announces that it filed a technical report under Canadian Securities Administrators'

National Instrument 43-101 Standard of Disclosure for Mineral Projects for the Waterbury Lake property in

the eastern portion of the Athabasca Basin of Northern Saskatchewan, Canada (the “Technical Report”).

The Technical Report is titled “Technical Report with an Updated Mineral Resource Estimate for the

Waterbury Lake Property, Northern Saskatchewan, Canada” with an effective date of December 21, 2018.

The Waterbury Lake property is owned by Denison (65.92%) and Korea Waterbury Uranium Limited

Partnership (“KWULP”) (34.06%), as limited partners, and Waterbury Lake Uranium Corporation (“WLUC”)

(0.02%), as general partner, in the Waterbury Lake Uranium Limited Partnership (“WLULP”). Denison is

the operator of the project and holds a 60% interest in WLUC.

The Waterbury Lake property is host to the J Zone deposit, discovered in 2010, and the Huskie deposit,

discovered by Denison in 2017. The Technical Report supports the disclosure of the maiden mineral

resource estimate for the Huskie deposit, and incorporates disclosure from a prior technical report dated

September 6, 2013 with the mineral resource estimate for the J Zone deposit.

The technical report is posted on the Company's website at www.denisonmines.com and is or will be

available under its profile on SEDAR at www.sedar.com and on EDGAR at www.sec.gov/edgar.shtml. This

report supports the disclosure made by the Company in the management’s discussion and analysis for the

three and nine months ended September 30, 2018 dated November 9, 2018 (the “MDA”) and in the related

press release of Denison dated November 12, 2018 (the “Press Release” and with the MDA, the

“Disclosure”). There are no material differences contained in the technical report from the information

previously disclosed in the Disclosure.

Qualified Persons

The disclosure of a scientific or technical nature regarding the Waterbury Lake property contained in this

news release was reviewed and approved by Dale Verran, MSc, P.Geo., Pr.Sci.Nat., Denison's Vice

President, Exploration, who is a Qualified Person in accordance with the requirements of NI 43-101.

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 27,

2018 filed under the Company's profile on SEDAR at www.sedar.com.

About Denison

Denison is a uranium exploration and development company with interests focused in the Athabasca Basin

region of northern Saskatchewan, Canada. In addition to its 90.0% owned Wheeler River project, which

ranks as the largest undeveloped high-grade uranium project in the infrastructure rich eastern portion of the

Athabasca Basin region, Denison's Athabasca Basin exploration portfolio consists of numerous projects

covering approximately 320,000 hectares. Denison's interests in the Athabasca Basin also include a 22.5%

ownership interest in the McClean Lake joint venture ("MLJV"), which includes several uranium deposits

and the McClean Lake uranium mill, which is currently processing ore from the Cigar Lake mine under a toll

milling agreement, plus a 25.17% interest in the Midwest and Midwest A deposits, and a 65.92% interest in

the J Zone and Huskie deposits on the Waterbury Lake property. Each of Midwest, Midwest A, J Zone and

Huskie are located within 20 kilometres of the McClean Lake mill.

Denison is also engaged in mine decommissioning and environmental services through its Denison

Environmental Services division and is the manager of Uranium Participation Corp., a publicly traded

company which invests in uranium oxide and uranium hexafluoride.

For more information, please contact

David Cates (416) 979-1991 ext. 362

President and Chief Executive Officer

Sophia Shane (604) 689-7842

Investor Relations

Follow Denison on Twitter @DenisonMinesCo

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this press release 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-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 results of, and estimates, assumptions and projections provided in, the

Technical Report; and Denison’s percentage interest in its projects and its agreements with its joint venture partners.

Statements relating to "mineral resources" are deemed to be forward-looking information, 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 believes that the expectations reflected in this forward-looking

information 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-looking events, please refer to the “Risk Factors” in Denison’s Annual Information

Form dated March 27, 2018 available under its profile at www.sedar.com and its Form 40-F available at

www.sec.gov/edgar.shtml. 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 its expectations except as otherwise required by

applicable legislation.