Denison Mines Corp. 2020 Annual Information Form March 26, 2021 ABOUT THIS ANNUAL INFORMATION FORM This annual information form (“AIF”) is dated March 26, Table of Contents 2021. Unless stated otherwise, all of the information in this AIF is stated as at December 31, 2020. About this AIF .................................... 1 About Denison ................................... 6 This AIF has been prepared in accordance with Canadian Developments over the Last Three securities laws and contains information regarding Years ................................................. 8 Denison’s history, business, mineral reserves and The Uranium Industry ........................ 17 resources, the regulatory environment in which Denison Mineral Resources and Reserves 24 does business, the risks that Denison faces and other Mineral Properties ............................. 27 important information for Shareholders. Athabasca Exploration: Sampling, Analysis and Data Verification ........... 102 This AIF incorporates by reference: Denison Operations ........................... 107 Manager of UPC ................................ 111 Denison’s management discussion and analysis (“MD&A”) for the year ended December 31, 2020, Denison Closed Mines Group ........... 112 Environmental, Health, Safety and Denison’s audited consolidated financial Sustainability Matters ........................ 112 statements for the year ended December 31, 2020, Government Regulation .................... 114 Risk Factors ...................................... 120 both of which are available under the Company’s profile Denison’s Securities .......................... 139 on SEDAR (www.sedar.com) and on EDGAR (www.sec.gov/edgar.shtml) as an exhibit to the Denison’s Management ..................... 140 Company’s Form 40-F. Legal and Regulatory Proceedings ... 146 Material Contracts ............................. 147 Names and Interests of Experts ........ 149 Financial Information Additional Information ........................ 150 Unless otherwise specified, all dollar amounts referred to Audit Committee Mandate ................. A in this AIF are stated in Canadian dollars (“CAD”). Glossary of Terms ............................. B References to “US$” or “USD” mean United States dollars. Financial information is generally derived from consolidated financial statements that have been prepared in accordance with International Financial Reporting Standards as issued by the International Accounting Standards Board. Caution about Forward-Looking Information Certain information contained in this AIF and the documents incorporated by reference concerning the business, operations and financial performance and condition of Denison constitutes forward-looking information within the meaning of the United States Private Securities Litigation Reform Act of 1995 and similar Canadian legislation. Generally, the use of words and phrases like "plans", "expects", "is expected", "budget", "scheduled", "estimates", “forecasts", "intends", "anticipates", or "believes", or the negatives and/or variations of such words and phrases, or statements that certain actions, events or results "may", "could", "would", "might" or "will" "be taken", "occur", "be achieved" or “has the potential to” and similar expressions are intended to identify forward-looking information. Forward-looking information involves known and unknown risks, uncertainties, material assumptions and other factors that may cause actual results or events to differ materially from those expressed or implied by such forward-looking statements. 2020 ANNUAL INFORMATION FORM 1 Denison believes that the expectations and assumptions reflected in this forward-looking information are reasonable, but no assurance can be given that these expectations will prove to be correct. Forward-looking information should not be unduly relied upon. This information speaks only as of the date of this AIF, and Denison will not necessarily update this information, unless required to do so by securities laws. Examples of Forward-Looking Information This AIF contains forward-looking information in a number of places, including statements pertaining to Denison’s: expectations regarding raising capital and licences under governmental and other uses of capital applicable regulatory regimes operational and business outlook, including estimates of its mineral reserves and mineral exploration, evaluation and development resources plans and objectives expectations about 2021 and future market plans for capital expenditure programs, prices, production costs and global uranium exploration and development expenditures supply and demand and reclamation costs and timing expectations regarding ongoing joint results of its Wheeler River PFS and plans arrangements and Denison's share of same with respect to the EA and FS process (each expectations regarding additions to its as defined below) mineral reserves and resources through results of its Waterbury PEA (as defined acquisitions and exploration below) and related plans and objectives expectations regarding the toll milling of expectations regarding future uranium prices Cigar Lake ores, and the relationships with its and/or applicable foreign exchange rates contractual partners with respect thereto expectations regarding the process for and future royalty and tax payments and rates receipt of regulatory approvals, permits and expectations regarding possible impacts of litigation and regulatory actions 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. Material Risks Denison's actual results could differ materially from those anticipated. Management has identified the following risk factors which could have a material impact on the Company or the trading price of its common shares (“Shares”): the capital intensive nature of mining industry dependence on obtaining licenses, and other and the uncertainty of funding regulatory and policy risks global financial conditions, including market uncertainty regarding engagement with reaction to COVID-19 and operational risks Canada’s First Nations and Métis related to the COVID-19 pandemic environment, health and safety risks the speculative nature of exploration and lack of public market for uranium and global development projects demand and international trade restrictions Denison’s history of negative cash flow the impact of uranium price volatility on the the imprecision of mineral reserve and valuation of Denison’s assets, including resource estimates mineral reserves and resources, and the the risks of, and market impacts on, market price of its Shares developing mineral properties uncertainty regarding public acceptance of risks associated with the selection of novel nuclear energy and competition from other mining methods energy sources 2020 ANNUAL INFORMATION FORM 2 volatility in the market price of the Company’s uncertainty as to reclamation and Shares decommissioning liabilities and timing the risk of dilution from future equity potential for technical innovation rendering financings Denison’s products and services obsolete devaluation of any physical uranium held by liabilities inherent in mining operations and the Company, and risk of losses, due to the adequacy of insurance coverage fluctuations in the price of uranium and/or the ability of Denison to ensure compliance foreign exchange rates with anti-bribery and anti-corruption laws dependence on other operators of the the uncertainty regarding risks posed by Company’s projects climate change reliance on uranium storage facilities the reliance of the Company on its reliance on contractors, experts and other information systems and the risk of cyber- third parties attacks on those systems the risk of failure to realize benefits from dependence on key personnel transactions potential conflicts of interest for the the risk of Denison’s inability to expand and Company’s directors who are engaged in replace its mineral reserves and resources similar businesses competition for properties limitations of disclosure and internal controls risk of challenges to property title and/or the potential influence of Denison’s largest contractual interests in Denison’s properties Shareholder, Korea Electric Power the risk of failure by Denison to meet its Corporation (“KEPCO”) and its subsidiary, obligations to its creditors Korea Hydro & Nuclear Power (“KHNP”). change of control restrictions The risk factors listed above are discussed in more detail later in this AIF (see “Risk Factors”). The risk factors discussed in this AIF are not, and should not be construed as being, exhaustive. Material assumptions The forward looking statements in this AIF and the documents incorporated by reference are based on material assumptions, including the following, which may prove to be incorrect: our budget, including expected exploration levels and costs and the assumptions regarding market conditions and other factors upon which we have based our expenditure expectations our ability to execute our business plans for 2021 and beyond our ability to, and the means by which the Company can, raise additional capital to advance other exploration and evaluation objectives our ability to obtain all necessary regulatory approvals, permits and licences for our planned activities under governmental and