Denison Announces Initiation of Environmental Impact Assessment Process and Execution of MOU with Local Communities FOR the Wheeler River Project

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

PRESS RELEASE

DENISON ANNOUNCES INITIATION OF ENVIRONMENTAL IMPACT ASSESSMENT

PROCESS AND EXECUTION OF MOU WITH LOCAL COMMUNITIES FOR THE

WHEELER RIVER PROJECT

Toronto, ON – June 3, 2019. Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:

NYSE American) is pleased to announce that the Canadian Nuclear Safety Commission ("CNSC") and the

Saskatchewan Ministry of Environment ("SK MOE") hav e accepted the Provincial Technical Proposal and

Federal Project Description (the “Project Description”) submitted by Denison for the In-Situ Recovery (“ISR”)

uranium mine and processing plant proposed for the Company’s 90% owned Wheeler River Project

(“Wheeler River” or the “Project”). Denison is also pleased to announce that it has executed a series of

Memoranda of Understanding (the “MOUs”) with Indigenous communities in support of the advancement

of the Project.

David Cates, President and CEO of Denison commented , “Acceptance of the Project Description by the

regulatory agencies is a critical first step for th e development of the Wheeler River Project. The Com pany

is excited to continue working with Indigenous communities, regulatory agencies, and the public during the

environmental assessment process – to achieve the C ompany’s objectives of advancing Wheeler River

through the Environmental Impact Assessment (“EIA”), regulatory approval, and feasibility study processes.

Successfully engaging, and entering into MOUs with local Indigenous communities, ahead of the initiati on

of the EIA process, signals strong support for the advancement of Wheeler River in future years. We lo ok

forward to building on the relationships that we’ve established over the past several years to develop a

collaborative vision for the future of the Project.”

Project Description

Acceptance of the Project Description is the first formal step to officially commence the EIA process in

accordance with the requirements of both the Canadian Environmental Assessment Act, 2012 (Canada)

(“CEAA 2012”) and The Environmental Assessment Act (Saskatchewan). The Project Description outlines

the major components of the Project and the potenti al interactions with the environment. The executiv e

summary of the Project Description is available in English, French, Dene and Cree on the Company’s

website at www.denisonmines.com .

The CNSC and the SK MOE are expected to carry out a coordinated Federal-Provincial EIA that will follow

the spirit of the Canada-Saskatchewan Agreement on Environmental Assessment Cooperation (2005), to

the extent possible. The cooperation agreement allows for the production of a single Environmental Impact

Statement for the Project (the “Project EIS”), whic h is intended to present the findings of the EIA in

accordance with the requirements of both levels of government. A successful EIA process is critical t o

securing the approvals necessary to develop and operate a mine in Canada.

The Company identified the EIA process as a key ele ment of the Project's critical path. Accordingly,

Denison plans to initiate various studies and assessments as part of the EIA process, which is intended to

culminate in the preparation of the Project EIS. Th e EIA is a planning and decision-making tool, which

involves predicting potential environmental effects throughout the project lifecycle (construction, operation,

decommissioning and post-decommissioning) at the si te, and within the local and regional assessment

areas. The EIA objectives are to minimize or avoid adverse environmental effects before they occur and

incorporate environmental factors into decision making processes. In addition to predictions made, effective

monitoring programs will be developed based on resu lts of the assessments and implemented as part of

the “plan, do, check, act” style system for continual improvement and adaptive management. The EIA work

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builds upon the comprehensive environmental baseline dataset Denison has prepared for the Project, and

feedback collected from engagement activities completed to date.

Environmental Advantages of the Proposed Wheeler Ri ver Project

After careful consideration of the strong economic results produced by the Pre-Feasibility Study ("PFS "),

prepared in accordance with NI 43-101 for the Proje ct in late 2018, Denison and the Wheeler River Join t

Venture (“WRJV”) approved plans to initiate the EIA process as well as the engineering studies and related

programs required to advance the development of an ISR mining operation, highlighted by the high-grade

Phoenix deposit, with an on-site processing plant (see Denison’s news release dated December 18, 2018).

As outlined within the Project Description, the Com pany’s evaluation of the ISR mining method has

identified several significant environmental and permitting advantages – particularly when compared to the

impacts associated with conventional uranium mining in Canada. The Project’s ISR mining operation is

expected to produce no tailings, generate very smal l volumes of waste rock, and has the potential for low

volumes or possibly no water discharge to surface water bodies, as well as the potential to use the existing

power grid to operate on a near zero carbon emissio ns basis. The proposed use of a freeze wall, to

encapsulate the ore zone and contain the mining solution used in the ISR operation, streamlines the mining

process, minimizes interaction with the environment , and facilitates controlled reclamation of the sit e at

decommissioning. Taken together, the Project has th e potential to be one of the most environmentally

friendly uranium mining and processing operations i n the world. Owing largely to these benefits,

engagement with local Indigenous communities, the p ublic, and federal and provincial representatives, to

date, has been encouraging regarding the use of ISR mining.

Community Support

As reported within the Project Description, Denison has executed a series of MOUs, in support of the

advancement of the Project, with a number of Indige nous communities who assert that the Project falls

partially or entirely within their traditional terr itories, and where traditional land use activities are currently

practiced within the local and regional area surrounding the Project.

These non-binding MOUs formalize the signing parties’ intent to work together in a spirit of mutual respect

and cooperation in order to collectively identify p ractical means by which to avoid, mitigate, or othe rwise

address potential impacts of the Project upon the e xercise of Indigenous rights, Treaty rights, and ot her

interests, as well as to facilitate sharing in the benefits that will flow from the Project. The MOUs provide a

process for continued engagement and information-sh aring and establish a platform to identify business ,

employment and training opportunities for the parties with respect to the Project.

About Wheeler River

Wheeler River is the largest undeveloped uranium pr oject in the infrastructure rich eastern portion of the

Athabasca Basin region, in northern Saskatchewan – including combined Indicated Mineral Resources of

132.1 million pounds U 3O8 at an average grade of 3.3% U 3O8, plus combined Inferred Mineral Resources

of 3.0 million pounds U 3O8 at an average grade of 1.7% U3O8. The project is host to the high-grade Phoenix

and Gryphon uranium deposits, discovered by Denison in 2008 and 2014, respectively, and is a joint

venture between Denison (90% and operator) and JCU (Canada) Exploration Company Limited (10%).

A PFS was completed in late 2018, considering the p otential economic merit of developing the Phoenix

deposit as an ISR operation and the Gryphon deposit as a conventional underground mining operation.

Taken together, the project is estimated to have mi ne production of 109.4 million pounds U 3O8 over a 14-

year mine life, with a base case pre-tax NPV of $1. 31 billion (8% discount rate), Internal Rate of Ret urn

("IRR") of 38.7%, and initial pre-production capita l expenditures of $322.5 million. The ISR operation

planned for the Project includes the mining of the Phoenix deposit, which is estimated to have a stand -

alone base case pre-tax NPV of $930.4 million (8% d iscount rate), IRR of 43.3%, initial pre-production

capital expenditures of $322.5 million, and industr y leading average operating costs of US$3.33/lb U 3O8.

The PFS is prepared on a project (100% ownership) and pre-tax basis, as each of the partners to the WRJV

are subject to different tax and other obligations.

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Further details regarding the PFS, including additional scientific and technical information, as well as after-

tax results attributable to Denison's ownership int erest, are described in greater detail in the NI 43 -101

Technical Report titled "Pre-feasibility Study for the Wheeler River Uranium Project, Saskatchewan,

Canada" dated October 30, 2018 with an effective da te of September 24, 2018. A copy of this report is

available on Denison's website and under its profil e on SEDAR at www.sedar.com and on EDGAR at

www.sec.gov/edgar.shtml.

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% owned Wheeler River Project, Denison’s

Athabasca Basin exploration portfolio consists of n umerous projects covering approximately 310,000

hectares. Denison’s interests in the Athabasca Basi n 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 fro m the Cigar Lake mine under a toll milling agreemen t,

plus a 25.17% interest in the Midwest and Midwest A deposits, and a 66.51% interest in the J Zone and

Huskie deposits on the Waterbury Lake property. Eac h 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

Qualified Persons

The disclosure of scientific and technical informat ion regarding the Wheeler River Project in this new s

release was reviewed and approved by Dale Verran, M Sc, P.Geo., Pr.Sci.Nat., the Company's Vice

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

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this news release constitutes ‘forward-looking information’, within the meaning of the applicable United

States and 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 terminolog y 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 r esults ‘may’, ‘could’, ‘would’, ‘might’ or ‘will be taken’, ‘occur’, ‘be achieved’ or ‘has

the potential to’.

In particular, this news release contains forward-looking information pertaining to the following: development and expansion plans and

objectives, including the results of the PFS and pl ans for the EA and other regulatory and feasibility study processes for Wheeler

River; expectations regarding Denison’s community engagement and MOUs with local communities; and expe ctations regarding its

joint venture ownership interests and the continuit y of its agreements with its partners. 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, uncert ainties and other factors that may cause the actual results, level of activity,

performance or achievements of Denison to be materi ally different from those expressed or implied by s uch forward-looking

statements. 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 a ccurate and results may differ materially from thos e 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 factors discussed in Denison’s Annual Information Form dated March 12, 2019 under the heading ‘Risk Factors’. These factors

are not, and should not be construed as being exhaustive.

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Accordingly, readers should not place undue relianc e on forward-looking statements. The forward-lookin g information contained in

this news 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 news release. Denison does not undertake any obligation to publicly update or revise

any forward-looking information after the date of t his news release to conform such information to act ual results or to changes in

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

Cautionary Note to United States Investors Concerni ng Estimates of Measured, Indicated and Inferred Mi neral Resources

and Probable Mineral Reserves: This news release may use the terms 'measured', 'i ndicated' and 'inferred' mineral resources.

United States investors are advised that while such terms have been prepared in accordance with the definition standards on mineral

reserves of the Canadian Institute of Mining, Metal lurgy and Petroleum referred to in Canadian Nationa l Instrument 43-101 Mineral

Disclosure Standards ("NI 43-101") and are recogniz ed and required by Canadian regulations, the United States Securities and

Exchange Commission ("SEC") does not recognize them. 'Inferred mineral resources' have a great amount of uncertainty as to their

existence, and as to their economic and legal feasibility. It cannot be assumed that all or any part of an inferred mineral resource will

ever be upgraded to a higher category. Under Canadi an rules, estimates of inferred mineral resources m ay not form the basis of

feasibility or other economic studies. United States investors are cautioned not to assume that all or any part of measured or

indicated mineral resources will ever be converted into mineral reserves. United States investors are also cautioned not to

assume that all or any part of an inferred mineral resource exists, or is economically or legally mine able. References to

estimates of mineral reserves in this news release have been prepared in accordance with NI 43-101. Th e definition of probable

mineral reserves used in NI 43-101 differs from the definition used by the SEC in the SEC's Industry Guide 7. Under the requirements

of the SEC, mineralization may not be classified as a "reserve" unless the determination has been made, pursuant to a "final" feasibility

study that the mineralization could be economically and legally produced or extracted at the time the reserve determination is made.

Denison has not prepared a feasibility study for th e purposes of NI 43-101 or the requirements of the SEC. Accordingly, Denison's

probable mineral reserves disclosure may not be com parable to information from U.S. companies subject to the reporting and

disclosure requirements of the SEC.