Osisko Mining Inc. (TSX:OSK) is pleased to provide new results from the ongoing drill program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. The 800,000 metre drill program combines definition, expansion and exploration drilling in and around the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall).

Significant new analytical results from 23 intercepts in 17 drill holes focused on infill and expansion drilling in the Lynx deposit are presented below. Osisko continues to extend the known Lynx zones of mineralization through the application of the Windfall geological model and as the density of drilling increases. The new results appear to demonstrate that the Lynx 4 Zone is developing a high-grade core similar to the Lynx 1 discovery zone.

• New infill drillholes are delineating a high-grade zone in Lynx 4 between sections 3925E and 4225E
• Lynx 4 demonstrates good continuity along 1350 metres strike between sections 2875E and 4225E.
• New drilling shows the potential extension of Lynx 6 by 725 metres to the south-west.

Highlights from the new results include: 415 g/t Au over 5.9 metres and 19.9 g/t Au over 8.8 metres in OSK-W-17-1166-W1; 43.7 g/t Au over 4.8 metres in OSK-W-17-1128; 25.1 g/t Au over 4.5 metres in OSK-W-17-1386; 46.3 g/t Au over 2.4 metres in OSK-W-17-909-W4; 26.1 g/t Au over 4.2 metres in OSK-17-W-1156; 42.1 g/t Au over 2.0 metres in OSK-W-17-931; 17.4 g/t Au over 4.8 metres in OSK-W-17-1166-W4; 11.8 g/t Au over 5.5 metres in OSK-W-17-958; and 23.4 g/t Au over 2.0 metres in OSK-W-17-1397. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Notes:

1. True widths are estimated at 65 – 80% of the reported core length interval. See “Quality Control” below.
2. Definitions: HW = Hanging Wall, VNCR = Crustiform Vein.

OSK-W-17-909-W4 intersected two intervals in Lynx 4: 8.96 g/t Au over 2.5 metres and 46.3 g/t Au over 2.4 metres. The first interval is composed of up to 10% irregular pyrite stringers at a sericitized contact between a gabbro and a rhyolite. The second interval is composed of 3% interstitial pyrite in silica flooding within strongly sericitized andesite.

OSK-W-17-931 intersected 42.1 g/t Au over 2.0 metres in Lynx 4. Mineralization is composed of 5% disseminated pyrite, 2% pyrite-tourmaline stringers and trace of pyrite-silica flooding within a strongly sericitized rhyolite.

OSK-W-17-958 intersected 11.8 g/t Au over 5.5 metres in Lynx 4. Mineralization is composed of 5% disseminated pyrite, and 2% pyrite-sphalerite stringers. Two low angle smoky quartz veins have local visible gold. The host rhyolite is strongly silicified and sericitized.

OSK-W-17-1054 intersected 12.9 g/t Au over 2.0 metres in Lynx 1. Mineralization is composed of 1% pyrite stringers within a chloritized shear zone.

OSK-W-17-1117 intersected 4.76 g/t Au over 2.1 metres in Lynx 2. Mineralization is composed of 8% pyrite-silica flooding and 1% pyrite stringers within a strongly silicified fragmental felsic dike.

OSK-W-17-1028 intersected 43.7 g/t Au over 4.8 metres in Lynx 2. Mineralization is composed of 2% pyrite stringers and local visible gold at the contact between a rhyolite and a gabbro. Silica, sericite and fuchsite alteration is pervasive in the rhyolite.

OSK-W-17-1156 intersected Lynx HW returning 26.1 g/t Au over 4.2 metres. Mineralization is composed of 5% pyrite stringers and 2% disseminated pyrite. Local visible gold, electrum and chalcopyrite are disseminated at the strongly silicified and fuchsitized contact between the gabbro and felsic intrusion.

OSK-W-17-1166-W1 intersected three intervals in Lynx 4: 19.9 g/t Au over 8.8 metres, 15.0 g/t Au over 2.1 metres and 415 g/t Au over 5.9 metres. The first interval is composed of 2% pyrite stringers and 1% ptygmatic tourmaline veins within a strongly silicified porphyritic felsic dike. Local visible gold is associated with pyrite-silica flooding. The second interval is composed of up to 4% pyrite silica flooding and 1% pyrite clusters within a strongly silicified, carbonatized and fuchsitized porphyric felsic dike. The last interval includes four high grade sub-intervals with up to 25% disseminated pyrite, up to 7% pyrite stringers and pyrite-tourmaline stringers. The mineralization is hosted in a strongly silicified rhyolite.

OSK-W-17-1166-W4 intersected 17.4 g/t Au over 4.8 metres in Lynx 4. Mineralization is composed of up to 7% disseminated pyrite. Local visible gold is within a low angle smoky quartz vein hosted in a strongly sericitized and silicified rhyolite. This interval extends Lynx 4 by 85 metres vertically under OSK-W-17-1166-W1 (this press release).

OSK-W-17-1190 intersected 13.6 g/t Au over 2.0 metres in Lynx 6. Mineralization is composed of 2% pyrite clusters and 1% pyrite stringers within a chloritized andesite. The interval is 725 metres up plunge and south-west of OSK-W-17-1343-W3 (this press release).

OSK-W-17-1199 intersected 3.68 g/t Au over 2.0 metres. Mineralization is composed of pyrite-silica flooding and quartz veins within a chloritized fragmental felsic dike.

OSK-W-17-1242-W1 intersected 9.36 g/t Au over 2.0 metres in Lynx HW. Mineralization is composed of 1% disseminated and clustered pyrite at the contact between a gabbro and a porphyritic felsic dike.

OSK-W-17-1265 intersected 3.19 g/t Au over 2.7 metres in Lynx 4. Mineralization is at the contact between a rhyolite and a felsic dike and composed of 1% pyrite stringers with strong sericite alteration.

OSK-W-17-1343-W2 intersected three intervals: 5.79 g/t Au over 2.2 metres and 14.2 g/t Au over 2.0 metres in Lynx 4 and 7.84 g/t Au over 2.1 metres in Lynx 6. The first interval is composed of up to 10% pyrite clusters and silica-carbonates-tourmaline veins within a moderately silicified and sericitized rhyolite. The second interval is composed of 10% pyrite-silica flooding within a strongly sericitized rhyolite. The last interval is composed of local visible gold, 3% disseminated pyrite and 2% pyrite clusters within a chloritized and silicified rhyolite. This interval extends Lynx 6 by 50 meters vertically under OSK-W-17-1128 (14.0 g/t Au over 2.3 metres previously reported October 12, 2017).

OSK-W-17-1386 intersected two intervals in Lynx 1: 18.1 g/t Au over 2.5 metres and 25.1 g/t Au over 4.5 metres. The first interval is composed of up to 3% pyrite clusters, 1% quartz-tourmaline veins and 1% disseminated pyrite. Mineralization is hosted in a sericitized and fuchsitized gabbro. The second interval is at the contact between a gabbro and a felsic dike. Mineralization is composed of 3% pyrite clusters, 3% pyrite-silica flooding and 1% pyrite stockwork.

OSK-W-17-1397 intersected Lynx 2 returning 23.4 g/t Au over 2.0 metres. Mineralization is composed of up to 10% pyrite-silica flooding, 2% disseminated pyrite and local visible gold within a fuchsite and sericite altered rhyolite.

OSK-W-17-1399 intersected 6.11 g/t Au over 5.2 metres in Lynx 1. Mineralization is composed of up to 10% pyrite stringers and 5% pyrite clusters associated with 30% quartz crustiform veins injected in a weak fuchsite altered gabbro.

Qualified Person

The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of the Windfall Lake gold project, who is a “Qualified Person” as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects.

Quality Control and Reporting Protocols

True widths determinations are estimated at 65-80% of the reported core length intervals for most of the zones. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at ALS Laboratories in Val d’Or, Québec, Thunder Bay and Sudbury, Ontario or Vancouver, British Colombia or Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control (“QA/QC”) and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Lake Gold Deposit

The Windfall Lake gold deposit is located between Val-d’Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by the previous operator comprises 2,762,000 tonnes at 8.42 g/t Au (748.000 ounces) in the indicated category and 3,512,000 tonnes at 7.62 g/t Au (860,000 ounces) in the inferred category (sourced from a technical report dated June 10, 2015 entitled “Preliminary Economic Assessment of the Windfall Lake Gold Property, Québec, Canada” with an effective date of April 28, 2015, prepared in accordance with NI 43-101). The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. The bulk of the mineralization occurs in the Main Zone, a southwest/northeast trending zone of stacked mineralized lenses, measuring approximately 600 metres wide and at least 1.400 metres long. The deposit is well defined from surface to a depth of 500 metres, and remains open along strike and at depth. Mineralization has been identified only 30 metres from surface in some areas and as deep as 870 metres in others, with significant potential to extend mineralization up and down-plunge and at depth.

About Osisko Mining Inc.

Osisko is a mineral exploration company focused on the acquisition, exploration, and development of precious metal resource properties in Canada. Osisko holds a 100% in the high-grade Windfall Lake gold deposit located between Val-d’Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding Urban Barry area and nearby Quevillon area (over 3,300 square kilometres), a 100% interest in the Marban project located in the heart of Québec’s prolific Abitibi gold mining district, and properties in the Larder Lake Mining Division in northeast Ontario, including the Jonpol and Garrcon deposits on the Garrison property, the Buffonta past producing mine and the Gold Pike mine property. The Corporation also holds interests and options in a number of additional properties in northern Quebec and Ontario. Osisko continues to be well financed with approximately $190 million in cash and investments.