HIGHLIGHTS

• Positive formal construction decision on the Cariboo Gold Project made by the Board of Directors, with an expected first gold pour in Q1 2029 and commercial production in H2 2029
• US$30 million strategic private placement from an affiliate of Trafigura, concentrate and doré off-take from Trafigura, and potential prepayment facility of up to US$120 million
• Go-forward capital obligation update for the Cariboo Gold Project of $990 million, supported by total available and proposed estimated sources of capital of up to $1,637 million, including $837 million in cash & equivalents

Project completion estimated at 22% as of July 31, 2026; Detailed engineering is approximately 40% complete; Procurement and commitments for long-lead items is progressing with an overall completion of approximately 44%; $325 million has been committed to date

Osisko Gold Group Inc. (NYSE: OGG, TSXV: OGG) is pleased to announce that its Board of Directors has made a formal positive decision to proceed with the construction of the Company’s 100%-owned Cariboo Gold Project, located in central British Columbia, Canada.

Sean Roosen, Chairman and CEO, commented: “The Board’s formal positive decision to commence full-scale construction of our flagship Cariboo Gold Project represents a defining milestone for Osisko Gold and a pivotal inflection point toward our objective of becoming an intermediate gold producer. This decision is a culmination of more than a decade of de-risking work on the Project, from early exploration when the first drills hit the ground in 2015, through permitting and technical studies, and into project financing and pre-construction. It reflects our confidence in the significant long-term value Cariboo can deliver to our shareholders and other stakeholders, and in the transformational impact it can have on the future of Osisko Gold. I’d like to commend our talented team for their professionalism, dedication and extensive contributions over the years that have brought us to this important milestone.”

“With this step forward, supported by our strong balance sheet position and other sources of available and proposed funding, our focus is now firmly on disciplined project execution toward first gold in early 2029. Based on an estimated remaining go-forward capital obligation of C$990 million and spot gold prices of US$4,350/oz, the Project demonstrates robust economics with after-tax NPV5% of C$3.2 billion, after-tax IRR of 42.7%, and average annual free cash flow of C$642 million in the first 5 years, underscoring its significant leverage to the gold price. Construction is expected to support 613 direct jobs at its peak, followed by 525 permanent jobs during operations, while generating substantial direct and indirect economic benefits for local communities and the Province of British Columbia. Bringing Cariboo through construction and into production represents only the first step in establishing a strong platform for the Company’s long-term growth strategy. In parallel, we continue to accelerate ongoing conversion drilling within the current deposit and advance exploration of the substantial potential at depth and along strike within the existing permit footprint, as well as across the broader Cariboo regional property. We look forward to providing further regular updates on our progress.”

Project Go-Forward Capital Obligation Estimate Update

The Project’s remaining go-forward capital obligation is estimated at $990 million, net of approximately $272 million in costs incurred up to and including July 31, 2026, inclusive of contingency of approximately 16.5%, and assuming the leasing of major mining equipment of approximately $117 million. Relative to the initial cost estimate outlined in the 2025 Optimized Feasibility Study (as defined herein), the go-forward update reflects costs incurred to date, progress achieved on detailed engineering and the procurement of major contracts, updates to certain cost assumptions to account for market inflation due to passage of time and broader industry and labour trends, inclusion of costs related to a PCM contract, and the reclassification of certain expenditures previously included in operating costs, principally those associated with the construction of the transmission line. The update also reflects certain modifications to the construction schedule, resulting in an anticipated 30-month construction period from August 1, 2026 (from 24 months in the 2025 FS) to first gold pour in Q1 2029 and 36 months (from 34 months in the 2025 FS) to commercial production in H2 2029.

1. From August 1, 2026.
2. Assuming a USD:CAD exchange rate of C$1.38 per US$1.00.
3. Underground mine and development costs already include an embedded contingency.
4. The pre-production period is defined as the period prior to the achievement of a minimum of 30 consecutive days of operations during which the mill operates at an average of at least 60% of nameplate throughput of 4,900 tpd. During this ramp-up phase operating costs are capitalized and netted against revenues.
5. Equipment lease financing includes certain assumptions on mining and other equipment contemplated under currently negotiated, non-binding term sheets, and remain subject to change as negotiations progress. The equipment leasing market remains robust, and the Company continues to evaluate opportunities that would enhance its financial flexibility throughout the construction period and thereafter.
6. Totals may not add up due to rounding.
7. In connection with the go-forward capital obligation update, the Company will undertake a normal course review of its non-financial assets relating to the Cariboo Gold Project in accordance with IFRS Accounting Standards as at September 30, 2026, as part of its third quarter 2026 financial results preparation. For the avoidance of doubt, any impairment charge, if any, would be non-cash in nature and would have no impact on the Company’s cash flows.

The estimated go-forward capital obligation is expected to be expended over the construction period set out below, based on an assumed USD:CAD exchange rate of C$1.38 per US$1.00. To mitigate financial exposures associated with the go-forward capital obligation, including currency and commodity risks, and to protect future operating cash flows, the Company may opportunistically contemplate entering into derivative contracts, such as put options.

1. Assuming a USD:CAD exchange rate of C$1.38 per US$1.00.
2. Capital spend percentage breakdown associated with capital cost items only, and excludes capitalized revenue in year 2029.
3. Partial year from August 1, 2026, onwards.

The Project is designed as a conventional, decline-accessed underground mining operation employing mechanized long-hole stoping mining methods, with paste backfill, to extract ore from gold-bearing vein corridors. Underground access is currently provided through the Cow portal, with development extending into the Lowhee and Cow deposit Zones. At the mine site complex, earthworks have commenced on the second underground access at the Valley Portal. Once established, the Valley Portal will provide a second development front and support critical path primary development access to the Valley and Shaft Zones, which host the majority of the Cariboo Gold deposit’s mineral reserves and mineral resources.

Approximately 3.0 kilometres of underground development has been completed to date. Early works have already commenced during pre-construction, with preparatory activities advancing at the mine site complex, waste rock storage facility, sediment control pond and water treatment plant, among other areas. Major earthworks are scheduled to ramp-up in Q3 2026 and are expected to continue through Q4 2027, with the process plant foundations work commencing in the summer of 2027 and building enclosure targeted for Q2 2028. The expected timeline to commercial production, including key milestones and work areas, is outlined in Figure 1 below:

FIGURE 1: Cariboo Gold Project Development Timeline to Commercial Production

Trafigura Financing and Commercial Agreements

As part of the Board’s decision to approve a final investment decision, the Company is pleased to announce that it and its wholly-owned subsidiary, Barkerville Gold Mines Ltd. have entered into agreements with Trafigura Canada Limited and Urion Investments Holdings Limited, an affiliate of Trafigura, that support the development of the Project.

The Trafigura Financing and Commercial Agreements comprises: (i) a subscription agreement between the Company and Urion pursuant to which Urion has agreed to acquire 9,554,141 common shares of the Company at a price of US$3.14 per Common Share representing a 10% premium to the five-day volume weighted average price of the Common Shares on the TSX Venture Exchange prior to signing, for gross proceeds of approximately US$30 million; (ii) offtake agreements between Barkerville and Trafigura for 100% of the (x) gold concentrate for the first four years of production at the Cariboo Gold Project (or until 80,000 dry metric tons of concentrate are delivered) and (y) gold doré for the first four years of production; and (iii) non-binding terms and an exclusivity period in respect of a potential subordinated gold prepayment facility and a further six-years of concentrate and doré offtake between Barkerville and Trafigura. The proposed Prepay Facility, as currently contemplated, doesn’t provide for any financial maintenance covenants, with final terms remaining subject to the execution of a definitive agreement.

Sean Roosen further commented: “We are very pleased to welcome Trafigura, a global leader in the commodities industry, as a long-term strategic partner at Cariboo. Its strategic investment in the Company reflects confidence in both the Project and our team’s ability to execute on its construction. We look forward to advancing towards a definitive agreement on the prepay financing, which would provide a significant additional non-dilutive source of capital for the construction of Cariboo.”

The proceeds of the Equity Investment will be used for the development of the Cariboo Gold Project. The Common Shares to be issued under the Equity Investment will be subject to a statutory hold period of four months and one day from the date of issuance pursuant to applicable Canadian securities laws. Closing of the Equity Investment remains subject to final acceptance of the TSX Venture Exchange and the New York Stock Exchange.

In connection with the Equity Investment, Urion has also agreed to enter into a voting support agreement with the Company, pursuant to which Urion will agree to vote its Common Shares in accordance with the recommendations of the board of directors or management of the Company, subject to certain exceptions. The Voting Support Agreement also contains customary standstill and lock-up provisions restricting Urion’s ability to acquire additional Common Shares or dispose of its Common Shares for specified periods.

The Offtake Agreements provide for the purchase by Trafigura of 100% of the gold concentrate and doré bars produced by Barkerville from the Cariboo Gold Project at prices that incorporate prevailing London Bullion Market Association and deductions including standard treatment and refining charges. Deliveries under the Offtake Agreements are expected to commence upon the start of first gold pour at the Cariboo Gold Project.

Barkerville and Trafigura have also agreed to non-binding terms in respect of a potential Prepay Facility of up to US$120 million and Trafigura has been granted an exclusivity period during which the parties will negotiate definitive documentation for such facility. There is no assurance that definitive documentation for the Prepay Facility will be entered into on the terms currently contemplated or at all. The non-binding terms contemplate that the Prepay Facility will be secured by a subordinated security interest against the assets of Barkerville. The facility is contemplated to be available to draw for three years from closing, with a maturity date that is at a minimum five years from closing at an interest rate of SOFR plus 6.00%.

Double Zero Capital LP an existing insider of the Company, has pre-emptive rights under the investor rights agreement dated August 15, 2025, between Double Zero and the Company to participate in the Equity Investment on the same terms as Urion, subject to the terms and conditions of the Double Zero IRA. Double Zero is entitled to participate in the Equity Investment on the same terms as Urion in order to maintain its existing ownership percentage in the Company. As of the date hereof, Double Zero has not waived its pre-emptive rights under the Double Zero IRA.

Closing of the Equity Investment is expected to occur in September 2026, subject to the satisfaction of customary closing conditions, including final acceptance of the TSX Venture Exchange and the New York Stock Exchange. The Equity Investment is not subject to any minimum subscription amount.

Sources and Uses of Capital

The Company intends to maintain a disciplined approach to capital allocation over the ensuing construction period, focused on preserving sufficient liquidity and financial flexibility through the Project’s construction, ramp-up and achievement of commercial production. The Company also intends to continue its infill and conversion drilling programs throughout the construction phase to further de-risk planned production areas by: (a) increasing geological confidence and definition of the existing measured and indicated mineral resources, and (b) supporting the upgrade of inferred mineral resources to higher confidence categories and, where appropriate, their potential conversion of such resources to mineral reserves after considering applicable modifying factors.

Table 3 summarizes the estimated sources and uses of capital from August 1, 2026 through to forecasted commercial production in H2 2029. Total sources of capital are estimated at approximately $1,637 million (US$1,186 million) and comprise current cash and cash equivalents, marketable securities, and project debt, and are subject to the successful closing of the Equity Investment, the execution of the related definitive agreement in connection with the gold prepay facility, and certain assumptions in relation to equipment financing. Estimated uses of capital are estimated at approximately $1,435 million (US$1,040 million) and include the remaining go-forward capital obligation, working capital, exploration expenditures, debt service and financing costs, and other general corporate expenditures. This results in projected surplus liquidity of approximately $201 million (US$146 million).

TABLE 3: Sources and Uses of Capital (from August 1, 2026 to commercial production)

 Adjusted working capital is as of June 30, 2026, and includes cash and cash equivalents of approximately $837 million, net of current liabilities.

1. Exploration expenditures include remaining flow-through expenditure obligations of approximately $22 million, with the balance related to planned exploration activities across conversion, infill, and CGP deeps exploration surface and underground drilling.

Additional potential sources not reflected in the estimated sources above include proceeds, if any, from the exercise of certain outstanding warrants of the Company. Full exercise of such warrants would generate potential proceeds of approximately US$120 million from the warrants expiring in August 2027 with an exercise price of US$2.56 per Common Share, which are subject to an acceleration provision beginning in mid-November 2026, and approximately US$150 million from warrants expiring in October 2029 with an exercise price of US$3.00 per Common Share. The Company continues to actively evaluate opportunities to optimize its project debt structure and reduce its overall cost of capital. The exercise of Company warrants is entirely at the discretion of the holders thereof, and there can be no assurance that any or all of the Company warrants will be exercised or that the Company will receive any proceeds therefrom.

Summary of Project Metrics

In connection with the Project’s go-forward capital obligation update, the Company has adjusted, where applicable, certain financial inputs in the Cariboo Technical Report (as defined herein) to reflect the Project’s current status and the prevailing commodity price environment, which have an impact on project economics. As noted above, the update also reflects certain modifications to the construction schedule, resulting in an anticipated 30-month construction period from August 1, 2026 (from 24 months in the 2025 FS) to first gold pour in Q1 2029 and 36 months (from 34 months in the 2025 FS) to commercial production in H2 2029.

Except for these adjustments, the information contained in the Cariboo Technical Report (as defined herein) relating to geology and mineralization, mineral reserves and mineral resources, mining methods and mineral processing, together with all other material assumptions and qualifications, remains current and unchanged. A summary of Project metrics is presented in Table 4:

1. Totals may not add up due to rounding. Spot pricing scenario is based on the LBMA gold price as of the close of business on September 11, 2026, rounded to nearest US$50/oz.
2. Non-IFRS Financial Measure. See Cautionary Statements – Non-IFRS Financial Measures.
3. Go-forward capital obligation associated with the August 2026 update assumes remaining capital costs from August 1, 2026 to commercial production. Refer to Table 1 for a more detailed breakdown.
4. Under the spot gold price scenario, higher pre-production revenues provide a greater offset to the go-forward capital obligation than under the long-term consensus pricing scenario.
5. Average free cash flow for the first 5 years is calculated for the periods between 2029 and 2034, inclusive of the pre-production period.

Cariboo Gold Project Update

Project Development Photos

A Media Snippet accompanying this announcement is available by clicking on this link.

ABOUT THE CARIBOO GOLD PROJECT

The Cariboo Gold Project is a permitted, 100%-owned feasibility-stage project located in the historic Wells-Barkerville mining camp of central British Columbia, Canada. Spanning approximately 186,740 hectares, the Company’s land package includes 443 mineral titles and covers an area that extends approximately 77-kilometres from northwest to southeast. In late 2024, the Project was granted the Mines Act and Environmental Management Act (British Columbia) permits, marking the successful completion of the permitting process for key approvals, solidifying the Project’s shovel-ready status.

Mineral Reserves Estimate – Cariboo Gold Project

The mineral reserves estimate for the Cariboo Gold Project included in the Cariboo Technical Report (as defined herein) has an effective date of April 10, 2025. Only mineral resources that were classified as measured and indicated were given economic attributes in the mine design, and when demonstrating economic viability were classified as mineral reserves.

Notes:

1. Totals may not add up due to rounding.
2. The mineral reserve estimate follows the 2014 CIM Definition Standards on Mineral Resources and Reserves and the 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.
3. Mineral reserves used the following assumptions: US$1,915/oz gold price, USD:CAD exchange rate of 1.32, and variable cut-off value from 1.70 g/t to 2.0 g/t Au
4. Mineral reserves include both internal and external dilution along with mining recovery. The external dilution is estimated to be 10.1%. The average mining recovery factor was set at 91.3% to account for ore left in each block in the margins of the deposit.

Mineral Resources Estimate – Cariboo Gold Project

The mineral resources estimate for the Cariboo Gold Project included in the Cariboo Technical Report (as defined herein) has an effective date of April 22, 2025, and is reported exclusive of mineral reserves. Mineral resources that are not mineral reserves do not have demonstrated economic viability. The reader is cautioned that inferred mineral resources have a greater degree of uncertainty than indicated mineral resources and must not be converted to mineral reserves; it is reasonably expected, though not guaranteed, that the majority of inferred mineral resources could be upgraded to indicated mineral resources with continued exploration.

Notes:

1. The independent and qualified persons for the mineral resources estimates, as defined by NI 43-101, are Carl Pelletier, P.Geo., and Tessa Scott, P.Geo. (Norda Stelo). The effective date of the mineral resource estimate included in the Cariboo Technical Report is April 22, 2025.
2. These mineral resources, exclusive of the reserves, are not mineral reserves and do not have demonstrated economic viability.
3. The mineral resources estimate follows the 2014 CIM Definition Standards on Mineral Resources and Reserves and the 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.
4. A total of 481 vein zones were modelled for the Cow Mountain (Cow and Valley), Island Mountain (Shaft and Mosquito), Barkerville Mountain (BC Vein, KL, and Lowhee) deposits and one gold zone for Bonanza Ledge. A minimum true thickness of 2.0 m was applied, using the gold grade of the adjacent material when assayed or a value of zero when not assayed.
5. The estimate is reported for a potential underground scenario at a cut-off grade of 1.8 g/t Au, except for Bonanza Ledge at a cut-off grade of 3.5 g/t Au. The cut-off grade for the Cow, Valley, Shaft, Mosquito, BC Vein, KL, and Lowhee deposits was calculated using a gold price of US$2,400/oz; a USDCAD exchange rate of 1.35; an underground mining cost of $66.3/t; a processing and transport cost of $30.80/t; a G&A plus Environmental cost of $22.40/t; and a sustaining CAPEX cost of $45.6/t. No changes have been applied for the Bonanza Ledge. The cut-off grade for the Bonanza Ledge deposit was calculated using a gold price of US$1,700/oz; a USDCAD exchange rate of 1.27; an underground mining cost of $79.13/t; a processing and transport cost of $65.00/t; and a G&A plus Environmental cost of $51.65/t. The cut-off grades may be re-evaluated in light of future prevailing market conditions (metal prices, exchange rate, mining cost, etc.).
6. Density values for Cow, Shaft, Lowhee, and BC Vein were estimated using the ID2 interpolation method, with a value applied for the non-estimated blocks of 2.80 g/cm3 for Cow, 2.78 g/cm3 for Shaft, 2.74 g/cm3 for Lowhee, and 2.69 g/cm3 for BC Vein. Median densities were applied for Valley (2.81 g/cm3), Mosquito (2.79 g/cm3), and KL (2.81 g/cm3). A density of 3.20 g/cm3 was applied for Bonanza Ledge.
7. A four-step capping procedure was applied to composited data for Cow (3.0 m), Valley (1.5 m), Shaft (2.0 m), Mosquito (2.5 m), BC Vein (2.0 m), KL (1.75 m), and Lowhee (1.5 m). Restricted search ellipsoids ranged from 7 to 50 g/t Au at four different distances ranging from 25 m to 250 m for each deposit. High grades at Bonanza Ledge were capped at 70 g/t Au on 2.0 m composited data.
8. The gold mineral resources for the Cow, Valley, Shaft, Mosquito, BC Vein, KL, and Lowhee vein zones were estimated using Datamine StudioTM RM 1.9 software using hard boundaries on composited assays. The dilution halo gold mineralization was estimated using Datamine StudioTM RM Pro 1.11. The OK method was used to interpolate a sub-blocked model (parent block size = 5 m x 5 m x 5 m). Mineral resources for Bonanza Ledge were estimated using GEOVIA GEMSTM 6.7 software using hard boundaries on composited assays. The OK method was used to interpolate a block model (block size = 2 m x 2 m x 5 m).
9. Results are presented in situ. Ounce (troy) = metric tons x grade / 31.10348. Calculations used metric units (metres, tonnes, g/t). The number of tonnes were rounded to the nearest thousand. Any discrepancies in the totals are due to rounding effects. Rounding followed the recommendations as per NI 43-101.
10. The qualified persons responsible for this section of this news release are not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other relevant factors that could materially affect the mineral resource estimate other than those disclosed in this news release and in the Cariboo Technical Report.

Technical Reports

Scientific and technical information relating to the Cariboo Gold Project and the 2025 feasibility study on the Cariboo Gold Project is supported by the technical report, titled “NI 43-101 Technical Report, Feasibility Study for the Cariboo Gold Project, District of Wells, British Columbia, Canada” dated June 11, 2025 (with an effective date of April 25, 2025).

For readers to fully understand the information in the Cariboo Technical Report, reference should be made to the full text of the Cariboo Technical Report in its entirety, including all assumptions, parameters, qualifications, limitations and methods therein. The Cariboo Technical Report is intended to be read as a whole, and sections should not be read or relied upon out of context. The Cariboo Technical Report was prepared in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects and is available electronically on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov) under Osisko Gold’s issuer profile and on the Company’s website at www.osiskogold.ca.

Qualified Persons

The scientific and technical information contained in this news release has been reviewed, verified and approved by Scott Smith, P. Geo., Vice President, Exploration of Osisko Gold, a “qualified person” within the meaning of NI 43-101.

Advisors

GenCap Mining Advisory is acting as debt advisor to Osisko Gold with Calagus AG acting as the Company’s advisor for its concentrate and doré.

Currency of Presentation and Exchange Rate Data

Dollar amounts set out in this news release are stated in Canadian dollars except as otherwise indicated. All references to “US$” or “U.S. dollars” are to the lawful currency of the United States and all references to “$,” “C$” or “Canadian dollars” are to the lawful currency of Canada. Unless otherwise indicated, amounts are based on an assumed USD:CAD exchange rate of C$1.38 per US$1.00.

ABOUT OSISKO GOLD GROUP INC.

Osisko Gold Group Inc. is a continental North American gold development company focused on past producing mining camps with district-scale potential. The Company’s objective is to become an intermediate gold producer through the development of its flagship, fully permitted, 100%-owned Cariboo Gold Project, located within the Company’s broader Cariboo regional land package in central British Columbia, Canada, which hosts numerous prospective exploration targets and provides opportunities for future discoveries. Its Cariboo project pipeline is complemented by the Tintic Project, located in the historic East Tintic mining district in Utah, U.S.A., a brownfield property with significant exploration potential, extensive historical mining data, and access to established infrastructure. Osisko Gold is focused on developing long-life mining assets in mining-friendly jurisdictions while maintaining a disciplined approach to capital allocation, development risk management, and mineral inventory growth.