Mr. Renaud Adams reports

IAMGOLD REPORTS INCREASE IN MINERAL RESERVES AND RESOURCES AT EXISTING ASSETS, WITH INCREASE IN RESOURCES AT GOSSELIN

Iamgold Corp. has updated its mineral reserves and mineral resources statement as of Dec. 31, 2023, prepared in accordance with National Instrument 43-101 (Standards of Disclosure for Mineral Projects). A summary table of the updated mineral resources and reserves for the company's current assets, including attributable ounces accounting for ownership interest, can be found herein.

Highlights:

• Updated Gosselin mineral resource estimate (100-per-cent basis) of 4.4 million indicated gold ounces in 161.3 million tonnes at 0.85 gram per tonne gold and 3.0 million inferred ounces (123.9 Mt at 0.75 g/t Au); this represents an estimated increase of 1.1 million ounces in indicated and 1.3 million ounces in inferred, representing a 32-per-cent and 74-per-cent increase, respectively; on an attributable basis (60.3 per cent), the Gosselin mineral resource estimate is 2.7 million ounces indicated and 1.8 million ounces inferred;
• Proven and probable mineral reserves (100-per-cent basis) of current assets increased 12 per cent to 11 million ounces of gold in 302 Mt at 1.14 g/t Au (7.8 million ounces attributable):
  • The Westwood mine complex mineral reserves increased 109 per cent to 1.2 million ounces (5.3 Mt at 7.14 g/t Au) as underground rehabilitation efforts over the course of the year allowed for the resumption of mining activities in previously closed zones;
• Measured and indicated mineral resources (100-per-cent basis) of current assets increased 16 per cent to 25.9 million ounces of gold in 811.7 Mt at 0.99 g/t Au (18.3 million ounces attributable):
• • Cote gold project M&I mineral resources (100-per-cent basis) increased 1.9 million ounces or 18 per cent to 12.1 million ounces in 444.8 Mt at 0.84 g/t Au (7.3 million ounce attributable);
• Gold price assumptions for mineral reserves were updated to $1,400 per ounce from $1,300 per ounce, and for mineral resources to $1,700 per ounce from $1,500 per ounce.

"The Iamgold exploration and operating teams have done an exceptional job over the past year, ensuring that we have replaced more than we mined during a period when our focus and capital was directed towards the upcoming ramp-up of Cote gold," said Renaud Adams, president and chief executive officer of Iamgold. "At Essakane, our teams continue to uncover additional value while managing the safety constraints of our operating footprint, while at Westwood, the growth in our reserves is a direct result of the tireless efforts of our teams and successes in the extensive redevelopment and rehabilitation of the mine.

"The updated resource at Gosselin is very exciting as the value of this deposit to the Cote project is clear. Gosselin is a large-scale deposit sitting immediately adjacent to Cote that, when combined, have an estimated measured and indicated mineral resource of 16.5 million ounces with an additional 4.2 million ounces of inferred, putting the project in exclusive company of large-scale Canadian assets. This year, we look forward to the continued drilling of Gosselin, targeting the potential connecting extensions of the breccias between the resource pits, as well as drilling beneath the mineralized envelopes to test the depth extensions and give some insights into the ultimate potential of these highly prospective deposits."

Proven and probable mineral reserves, on a 100-per-cent basis for current assets, were estimated at 11.0 million ounces of gold (7.8 million ounces attributable) as of Dec. 31, 2023, which were a 12-per-cent increase or 1.2 million ounces from the year prior. Mineral reserves at Essakane and Westwood increased 143,000 ounces and 632,000 ounces, respectively, for a combined 775,000 ounces, more than offsetting reserve depletion from mining of 453,000 ounces last year on a 100-per-cent basis.

Essakane P&P mineral reserves, on a 100-per-cent basis, increased an estimated 7 per cent from the year prior to 2.2 million ounces (2.0 million ounces attributable) at an average grade of 1.10 g/t Au. Probable mineral reserves (open pit) were estimated, on a 100-per-cent basis, at 1.8 million ounces (1.6 million ounces attributable) at an average grade of 1.32 g/t Au. On Dec. 18, 2023, Iamgold announced an updated mineral resource and reserve estimate for Essakane that was prepared in accordance with the disclosure requirements of National Instrument 43-101 and had an effective date of Sept. 30, 2023. Relative to this date, Essakane P&P mineral reserves decreased 144,000 ounces reflective of operating activities conducted in the fourth quarter.

Westwood mineral reserves, including the Grand Duc open pit, increased 109 per cent from 582,000 ounces to 1.2 million ounces, net of depletion, with grades increasing 26 per cent to 7.14 g/t Au. Excluding Grand Duc, underground mineral reserves were estimated at 1.1 million ounces at an average grade of 10.6 g/t Au. The increase in mineral reserves was driven by the rehabilitation efforts over the course of the year, which allowed for the resumption of mining activities in previously closed zones. The company plans to file an updated NI 43-101 technical report in the second half of the year, detailing the results of certain mine optimization efforts and strategic assessments of the Westwood complex.

Cote gold mineral reserves, on a 100-per-cent basis, increased 6 per cent, or 436,000 ounces, to 7.6 million ounces, with grades increasing 5 per cent to 1.01 g/t Au. On an attributable basis of 60.3-per-cent ownership in the joint venture with Sumitomo Metals Mining Co. Ltd., Cote gold mineral reserves were estimated at 4.6 million ounces. The increase in ounces was driven by the increased grade of proven mineral reserves to 1.09 g/t Au based on an increase in stockpiled inventory and the continuing grade control drilling program, with minimal impact from the gold price assumption increase to $1,400 per ounce as the tailings management facility is the primary constraint on the mineral reserves estimate.

A $1,400-per-ounce gold price assumption was used in the 2023 mineral reserve estimate as of Dec. 31, 2023, for Essakane and Cote gold, an increase from the prior-year assumption of $1,300 per ounce. The Westwood underground mineral reserve gold price assumption was unchanged at $1,300 per ounce.

Mineral resources

Measured and indicated mineral resources (inclusive of mineral reserves and on a 100-per-cent basis) for Iamgold's current assets increased 16 per cent or 3.6 million ounces to a total of 25.9 million ounces as of Dec. 31, 2023 (18.3 million ounces attributable). M&I mineral resource average grades remained essentially flat year over year at 0.99 g/t Au. The increase in total ounces can be primarily attributed to the increase in M&I mineral resources at Cote gold and Gosselin.

Global inferred mineral resources (on a 100-per-cent basis) declined 10 per cent, or 1.1 million ounces, to a total of 10.1 million ounces as of Dec. 31, 2023 (7.4 million ounces attributable). The decline in ounces is primarily associated with the upgrading of resource classification to M&I at Cote gold, which offset increases at Gosselin, Nelligan and Essakane. Inferred mineral resources have a great amount of uncertainty as to their grade and quantity because they are based on limited geological evidence. It cannot be assumed that all or part of the inferred mineral resources will ever be upgraded to a higher category or converted to mineral reserves.

The company assumed a gold price of $1,700 per ounce for estimating mineral resources as of Dec. 31, 2023, at Essakane, Cote gold, Gosselin, Nelligan and Gossey. Westwood mineral resources were estimated using a $1,600-per-ounce gold price. Monster Lake and Diakha-Siribaya mineral resources were estimated using a $1,500-per-ounce gold price, unchanged from the prior year.

Essakane M&I mineral resources, inclusive of mineral reserves and on a 100-per-cent basis, increased 19 per cent to an estimated 3.4 million ounces (3.1 million ounces attributable) as of Dec. 31, 2023, with grades increasing 19 per cent to 1.21 g/t Au. Inferred mineral resources increased 265 per cent or 285,000 ounces from the year prior with grades essentially remaining flat at an estimated 1.46 g/t Au. On Dec. 18, 2023, Iamgold announced an updated mineral resource and reserve estimate for Essakane that was prepared in accordance with the disclosure requirements of NI 43-101 and had an effective date of Sept. 30, 2023. Relative to this date, Essakane M&I mineral resources decreased 127,000 ounces reflective of mining activities conducted in the fourth quarter, while inferred mineral resources were estimated to be relatively unchanged.

Westwood M&I mineral resources, inclusive of mineral reserves, increased 6 per cent to 2.4 million ounces as of Dec. 31, 2023, with a modest increase in grades to 8.96 g/t Au. Inferred mineral resources declined 31 per cent to 743,000 ounces as estimated grades increased 28 per cent to 15.78 g/t Au.

Cote gold M&I mineral resources, inclusive of mineral reserves and on a 100-per-cent basis, increased 18 per cent or 1.9 million ounces to 12.1 million ounces (7.3 million ounces attributable), with grades decreasing only 3 per cent to 0.84 g/t Au. Inferred mineral resources decreased 69 per cent to 1.2 million ounces at estimated grades of 0.61 g/t Au as a result of the conversion of inferred mineral resource to indicated from the continuing grade control drill programs.

Nelligan M&I mineral resources, on a 100-per-cent basis, remained relatively flat at an estimated two million ounces averaging 0.84 g/t Au. Inferred ounces increased 8 per cent or 289,000 ounces to a total of an estimated 3.9 million ounces at average grades of 0.85 g/t Au. On Feb. 13, 2024, Iamgold announced the successful completion of the previously announced transaction with Vanstar Mining Resources Inc. whereby Iamgold has acquired all of the issued and outstanding common shares of Vanstar pursuant to a court-approved plan of arrangement. As a result of the arrangement, Iamgold now owns a 100-per-cent interest in the Nelligan gold project, located 60 kilometres southwest of Chibougamau, Que., Canada.

Gosselin

The Gosselin deposit, located immediately adjacent to the Cote gold pit, returned an updated mineral resource estimate, on a 100-per-cent basis, as of Dec. 31, 2023, of 4.4 million indicated gold ounces in 161.3 Mt at 0.85 g/t Au (2.7 million ounces attributable) and 3.0 million inferred ounces in 123.9 Mt at 0.75 g/t Au (1.8 million ounces attributable). This represents an estimated increase of 1.1 million ounces in indicated and 1.3 million ounces in inferred, representing a 32-per-cent and 74-per-cent increase, respectively. Combining the Gosselin and Cote deposits together results in a total measured and indicated mineral resource estimate for the Cote gold project of 16.5 million ounces with an additional 4.2 million ounces of inferred.

The company announced a maiden mineral resource estimate for the Gosselin deposit in October, 2021, which incorporated 163 diamond drill holes totalling 54,775 metres. The 2023 updated mineral resource estimate incorporated an additional 57 diamond drill holes totalling 34,790 metres. Drilling to date suggests the Gosselin deposit has the potential to approach similar dimensions as the adjacent Cote deposit. Drill intercepts obtained from the newly discovered West Breccia have significantly expanded this breccia body, which measures 250 metres by 170 metres and extends for a depth of approximately 400 metres. This has helped to highlight a highly prospective corridor at depth measuring up to 850 metres in strike length that remains to be tested between the Gosselin West breccia and the Cote deposit hydrothermal breccia. This represents a priority exploration opportunity to further expand the Gosselin resource below the 600-metre vertical depth extent of the current 2023 resources pit shell.

About Iamgold Corp.

Iamgold is an intermediate gold producer and developer based in Canada with operating mines in North America and West Africa. The company is building the large-scale, long-life Cote gold project in Canada in partnership with Sumitomo, which is expected to commence production in early 2024. In addition, the company has an established portfolio of early-stage and advanced exploration projects within high-potential mining districts in Canada. Iamgold employs approximately 3,600 people and is committed to maintaining its culture of accountable mining through high standards of environmental, social and governance practices, including its commitment to zero harm, in every aspect of its business. Iamgold is listed on the New York Stock Exchange (IAG) and the Toronto Stock Exchange (IMG), and is one of the companies on the Jantzi Social Index, a socially screened market-capitalization-weighted index consisting of companies which pass a set of broadly based environmental, social and governance rating criteria.

Qualified person and technical information

The company's mineral reserves are composed of in-place material -- that is, material containing ounces of gold for which an assessment of key modifying factors such as mining, processing, metallurgical recovery, infrastructure, economic, legal, environmental, social and governmental factors are used to determine their economic viability.

There are numerous limits inherent in estimating proven mineral reserves and probable mineral reserves, including many factors beyond the company's control. The estimation of mineral reserves is a subjective process, and the accuracy of any mineral reserves estimate is a function of the quality of available data and of engineering and geological interpretation and judgment. Results from drilling, testing and production, as well as material changes in metal prices subsequent to the date of an estimate, may justify a revision of such estimates.

Lisa Ragsdale, director, mining geology, Iamgold, is the qualified person for the purposes of National Instrument 43-101 with respect to the mineralization being reported on and is responsible for the review and approval of all mineral resources estimates for Iamgold. Guy Bourque, director, mining, Iamgold, is the QP responsible for the review and approval of all mineral reserves estimates for Iamgold. The technical information in this news release has been included with the consent and prior review of Ms. Ragsdale and Mr. Bourque, as applicable. The QPs have verified the data disclosed and data underlying the information or opinions contained in this news release.

For each of the projects and properties it operates, the company has established rigorous methods and procedures aimed at assuring reliable estimates of its mineral reserves and resources. For each mine and project, the relevant QPs verified the data incorporated, including sampling, analytical and test data underlying the information contained in this news release. Quality control falls under the responsibility of Ms. Ragsdale and Mr. Bourque.

In estimating mineral reserves, cut-off grades are established using the company's long-term metal price and foreign exchange assumptions, the average metallurgical recovery rates and estimated production costs over the life of the related operation. As part of the annual mineral reserve estimation process, the cost models used for cut-off grade calculations are compared with prior studies or estimates and are updated appropriately based on actual operating performance and price projections for inputs. For an underground operation, a cut-off grade is calculated for each mining method as production costs vary from one method to another. For a surface operation, production costs are determined for each block included in the block model of the relevant operation.

The nature of mining activities is such that the extraction of ore from a mine reduces mineral reserves. To renew mineral reserves (at least partially) on most of its producing properties, the company carries out exploration drilling programs at depth and laterally.

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