RK-25-254 and RK-25-256 (both intersecting 2.0 and 2.1 m of off-scale (>61,000 cps)) are located 51 m and 119 m away from RK-25-232 (15 m at 15.9% U₃O₈).

Results highlight the repetition of upgrading high-grade shoots within growing mineralized footprint.

The following new holes intersected broad intercepts of cumulative mineralization (>500cps):

• RK-25-246: 20.5m including 2.5m >10,000cps
• RK-25-247: 18.0m including 2.5m >10,000cps
• RK-25-251: 9.5m
• RK-25-254: 19.5m including 5.0m >10,000cps including 2.0m >61,000cps
  RK-25-256: 10.0m including 3.3m >10,000cps including 2.1m >61,000cps

Vancouver, British Columbia--(Newsfile Corp. - August 28, 2025) - NexGen Energy Ltd. (TSX: NXE) (NYSE: NXE) (ASX: NXG) ("NexGen" or the "Company") is pleased to announce continued exciting results from the summer drill program at the rapidly advancing PCE. Step-out holes RK-25-254 and RK-25-256 intersected 2.0 m and 2.1 m of cumulative >61,000 counts per second (cps), respectively, located 51 m up-dip and 119 m down-dip of PCE's best hole to date, RK-25-232 (Figures 1 and 2). These represent the best holes from the summer program to date and validate the growth in high-grade continuity. Overall, an upgraded high-grade shoot plunges a minimum 200 m from RK-25-254 to RK-24-222 as part of an emerging interpreted pattern of high-grade shoots spaced 70 m apart (Figures 2 and 3).

Depth of the intense high-grade in RK-25-254, at just 454.4 m depth, ranks among the shallowest intersections of massive uranium ever drilled by NexGen. Mineralization is open 300 m up-dip and completely contained in the competent basement rock, consistent with Arrow. Strong continuity of grade across the mineralized footprint is consistent with Arrow's basement-hosted uranium veins.

Drilling is also extending deeper where strongly developed alteration and structural disruption persist as key indicators of additional mineralization. Further significant expansion potential at PCE remains with mineralization open in most directions.

A total to 21,968.9 m of the planned 43,000m program has been drilled in 2025. Since discovery (see March 11, 2024, news release), 79 drillholes totalling 53,088.9 m have been completed (Figure 4). High-grade growth and overall mineralized extent are the focus with many more targets to be tested across this rapidly developing and growing high-grade system. 48 of the 79 drillholes are mineralized, including 34 intersecting high-grade (>10,000 cps) and 14 intersecting off-scale (>61,000 cps).

Leigh Curyer, Chief Executive Officer, commented: "This program is delivering exactly what we look for in a generational uranium discovery, basement-hosted significant mineralized system, continuity of high-grade mineralization, and growth potential. PCE is evolving in real time into a world-class system in its own right. NexGen's highly prospective land package continues to demonstrate exciting results and unmatched opportunity for Canada to take its place as the number one source of uranium in the world."

Jason Craven, Vice President, Exploration, commented: "NexGen's summer drill program is off to a fantastic start. PCE continues to deliver intense high-grade uranium at shallower depths than the world class Arrow deposit only 3.5km away. Early summer drilling results are building on emerging interpretations that include systematic repetition of high-grade shoots within the overall mineralized footprint, indicating potential for significant expansion at PCE."

Figure 1: RK-25-254 and RK-25-256 core photos of focused vein intercepts 170 m apart from one another, each having 2 m of massive replacement style uranium mineralization, with elevated radioactivity above and below what is shown; yellow outlines >1,000 cps, red outlines >10,000 cps, >61,000 cps outlined in purple.

Figure 2: Close-up of long section view of PCE high-grade subdomain around RK-25-232 (15.0 m at 15.9% U₃O₈)

Figure 3: Interpreted model of mineralization at PCE (as of this release) with newly interpreted high-grade shoots shown; view is a long section that looks perpendicular to the primary mineralized plane; total mineralized footprint in orange and the high-grade subdomains in red

Figure 4: Interpreted 3D model of PCE shown looking northwest (across strike) and northeast (along strike)

Table 1: 2025 Spectrometer results from summer drilling

• All depths and intervals are meters downhole, true thicknesses are yet to be determined.
• "Off-scale" refers to >61,000 cps (counts per second) readings by gamma spectrometer type RS-125.
• "Anomalous" means >500 cps readings by gamma spectrometer type RS-120.
• Where "CPS Range" is <500 cps, this refers to local low radioactivity within the overall interval.
• Unconformity of 'N/A' denotes a lack of visible contact between Athabasca sandstone and basement rock.
• Maximum internal dilution 2.0 m downhole.
• All depths and intervals are meters downhole, true thicknesses are yet to be determined. Resource modelling in conjunction with an updated mineral resource estimate is required before true thicknesses can be determined.

About NexGen

NexGen Energy is a Canadian company focused on delivering clean energy fuel for the future. The Company's flagship Rook I Project is being optimally developed into the largest low-cost producing uranium mine globally, incorporating the most elite environmental and social governance standards. The Rook I Project is supported by an N.I. 43-101 compliant Feasibility Study, which outlines the elite environmental performance and industry-leading economics. NexGen is led by a team of experienced uranium and mining industry professionals with expertise across the entire mining life cycle, including exploration, financing, project engineering and construction, operations and closure. NexGen is leveraging its proven experience to deliver a Project that leads the entire mining industry socially, technically and environmentally. The Project and prospective portfolio in northern Saskatchewan will provide generational, long-term economic, environmental, and social benefits for Saskatchewan, Canada, and the world.

NexGen is listed on the Toronto Stock Exchange, the New York Stock Exchange under the ticker symbol "NXE," and on the Australian Securities Exchange under the ticker symbol "NXG," providing access to global investors to participate in NexGen's mission of solving three major global challenges in decarbonization, energy security and access to power. The Company is headquartered in Vancouver, British Columbia, with its primary operations office in Saskatoon, Saskatchewan.

Technical Disclosure*

All technical information in this news release has been reviewed and approved by Jason Craven, NexGen's Vice President, Exploration, a qualified person under National Instrument 43-101.

Natural gamma radiation in drill core reported in this news release was measured in counts per second (cps) using a Radiation Solutions Inc. RS-125 gamma spectrometer. The reader is cautioned that total count gamma readings may not be directly or uniformly related to uranium grades of the rock sample measured; they should be used only as a preliminary indication of the presence of radioactive minerals.

A technical report in respect of the FS is filed on SEDAR (www.sedarplus.ca) and EDGAR (www.sec.gov/edgar.shtml) and is available for review on NexGen Energy's website (www.nexgenenergy.ca).

Cautionary Note to U.S. Investors

This news release includes Mineral Reserves and Mineral Resources classification terms that comply with reporting standards in Canada and the Mineral Reserves and the Mineral Resources estimates are made in accordance with NI 43-101. NI 43-101 is a rule developed by the Canadian Securities Administrators that establishes standards for all public disclosure an issuer makes of scientific and technical information concerning mineral projects. These standards differ from the requirements of the Securities and Exchange Commission ("SEC") set by the SEC's rules that are applicable to domestic United States reporting companies. Consequently, Mineral Reserves and Mineral Resources information included in this news release is not comparable to similar information that would generally be disclosed by domestic U.S. reporting companies subject to the reporting and disclosure requirements of the SEC Accordingly, information concerning mineral deposits set forth herein may not be comparable with information made public by companies that report in accordance with U.S. standards.

Forward-Looking Information

The information contained herein contains "forward-looking statements" within the meaning of applicable United States securities laws and regulations and "forward-looking information" within the meaning of applicable Canadian securities legislation. "Forward-looking information" includes, but is not limited to, statements with respect to mineral reserve and mineral resource estimates, the 2021 Arrow Deposit, Rook I Project and estimates of uranium production, grade and long-term average uranium prices, anticipated effects of completed drill results on the Rook I Project, planned work programs, completion of further site investigations and engineering work to support basic engineering of the project and expected outcomes. Generally, but not always, forward-looking information and statements can be identified by the use of words such as "plans", "expects", "is expected", "budget", "scheduled", "estimates", "forecasts", "intends", "anticipates", or "believes" or the negative connotation thereof or variations of such words and phrases or state that certain actions, events or results "may", "could", "would", "might" or "will be taken", "occur" or "be achieved" or the negative connotation thereof. Statements relating to "mineral resources" are deemed to be forward-looking information, as they involve the implied assessment that, based on certain estimates and assumptions, the mineral resources described can be profitably produced in the future.

Forward-looking information and statements are based on the then current expectations, beliefs, assumptions, estimates and forecasts about NexGen's business and the industry and markets in which it operates. Forward-looking information and statements are made based upon numerous assumptions, including among others, that the mineral reserve and resources estimates and the key assumptions and parameters on which such estimates are based are as set out in this news release and the technical report for the property , the results of planned exploration activities are as anticipated, the price and market supply of uranium, the cost of planned exploration activities, that financing will be available if and when needed and on reasonable terms, that third party contractors, equipment, supplies and governmental and other approvals required to conduct NexGen's planned exploration activities will be available on reasonable terms and in a timely manner and that general business and economic conditions will not change in a material adverse manner. Although the assumptions made by the Company in providing forward looking information or making forward looking statements are considered reasonable by management at the time, there can be no assurance that such assumptions will prove to be accurate in the future.

Forward-looking information and statements also involve known and unknown risks and uncertainties and other factors, which may cause actual results, performances and achievements of NexGen to differ materially from any projections of results, performances and achievements of NexGen expressed or implied by such forward-looking information or statements, including, among others, the existence of negative operating cash flow and dependence on third party financing, uncertainty of the availability of additional financing, the risk that pending assay results will not confirm previously announced preliminary results, conclusions of economic valuations, the risk that actual results of exploration activities will be different than anticipated, the cost of labour, equipment or materials will increase more than expected, that the future price of uranium will decline or otherwise not rise to an economic level, the appeal of alternate sources of energy to uranium-produced energy, that the Canadian dollar will strengthen against the U.S. dollar, that mineral resources and reserves are not as estimated, that actual costs or actual results of reclamation activities are greater than expected, that changes in project parameters and plans continue to be refined and may result in increased costs, of unexpected variations in mineral resources and reserves, grade or recovery rates or other risks generally associated with mining, unanticipated delays in obtaining governmental, regulatory or First Nations approvals, risks related to First Nations title and consultation, reliance upon key management and other personnel, deficiencies in the Company's title to its properties, uninsurable risks, failure to manage conflicts of interest, failure to obtain or maintain required permits and licences, risks related to changes in laws, regulations, policy and public perception, as well as those factors or other risks as more fully described in NexGen's Annual Information Form dated March 6, 2024 filed with the securities commissions of all of the provinces of Canada except Quebec and in NexGen's 40-F filed with the United States Securities and Exchange Commission, which are available on SEDAR at www.sedarplus.ca and Edgar at www.sec.gov.

Although the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in the forward-looking information or statements or implied by forward-looking information or statements, there may be other factors that cause results not to be as anticipated, estimated or intended. Readers are cautioned not to place undue reliance on forward-looking information or statements due to the inherent uncertainty thereof.

There can be no assurance that forward-looking information and statements will prove to be accurate, as actual results and future events could differ materially from those anticipated, estimated or intended. Accordingly, readers should not place undue reliance on forward-looking statements or information. The Company undertakes no obligation to update or reissue forward-looking information as a result of new information or events except as required by applicable securities laws.