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 19 intercepts in 12 drill holes and 5 wedges focused on infill drilling in the Lynx deposit are presented below. Today’s infill drilling results will not be included in the pending mineral resource scheduled for release in May 2018.

Highlights from the new results include: 115 g/t Au over 8.4 metres in OSK-W-17-1363; 58.7 g/t Au over 5.1 metres in OSK-W-17-1343-W1; 118 g/t Au over 2.5 metres and 85.1 g/t Au over 2.0 metres in OSK-W-17-1169-W2; 72.8 g/t Au over 3.1 metres in OSK-W-17-1166; 68.8 g/t Au over 2.0 metres in OSK-W-17-928; 67.0 g/t Au over 2.0 metres in OSK-W-17-1396; 50.3 g/t Au over 2.3 metres in OSK-W-17-986; and 43.0 g/t Au over 2.6 metres in OSK-W-17-1320. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

OSK-W-17-928 intersected 68.8 g/t Au over 2.0 metres in Lynx HW. Mineralization contains trace disseminated pyrite within a moderate sericite and weak silica altered rhyolite.

OSK-W-17-986 intersected a crustiform vein returning 50.3 g/t Au 2.3 metres. Mineralization contains local visible gold, 2% pyrite stringers, 2% crustiform quartz-carbonate veins and pyrite-silica flooding within a silica, carbonate and fuchsite altered gabbro.

OSK-W-17-1166 intersected 72.8 g/t Au over 3.1 metres in Lynx 4. Mineralization contains local visible gold, 10% pyrite-silica flooding and 3% pyrite-tourmaline stringers within a porphyritic felsic dike.

OSK-W-17-1320 intersected 43.0 g/t Au over 2.6 metres in Lynx. Mineralization contains 1% disseminated pyrite and trace pyrite in quartz veins within in a strong chlorite, moderate silica and weak sericite altered porphyritic felsic dike.

OSK-W-17-1343-W1 intersected 58.7 g/t Au over 5.1 metres in Lynx HW. Mineralization contains 3% pyrite-silica flooding, 1% pyrite-tourmaline stringers and a 10 centimetres quartz vein within a strong silica and moderate sericite altered porphyritic felsic dike.

OSK-W-17-1363 intersected 115 g/t Au over 8.4 metres in Lynx 2. Mineralization contains local visible gold and electrum and up to 25% disseminated pyrite or pyrite-tourmaline stringers within strong pervasive silica flooding. The gabbro host is strongly fuchsite and silica altered.

OSK-W-17-1396 intersected 67.0 g/t Au over 2.0 metres in Lynx 4. Mineralization contains 1% pyrite in quartz-tourmaline veins and 3% disseminated pyrite within a moderate sericite, moderate fuchsite and weak silica altered rhyolite.

OSK-W-18-1169-W1 intersected 7.84 g/t Au over 2.1 metres in Lynx 2. Mineralization contains 2% pyrite disseminated or as stringers and 10% quartz-carbonate and tourmalines veins within a silica and fuchsite altered gabbro.

OSK-W-18-1169-W2 intersected three intervals in Lynx 4: 118 g/t Au over 2.5 metres, 4.09 g/t Au over 2.0 metres and 85.1 g/t Au over 2.0 metres. The first interval contains local visible gold, up to 15% pyrite-tourmaline stringers and 1% disseminated pyrite within strong pervasive silica alteration at the contact between a silicified and sericitized gabbro and a sericitized rhyolite. The second interval contains local visible gold and 10% pyrite in smoky-quartz veins within a sericite altered rhyolite. The third interval contains local visible gold and 5% pyrite-tourmaline stringers within a strong silica, moderate sericite, moderate ankerite and weak fuchsite altered rhyolite.

OSK-W-18-1367-W2 intersected 4.55 g/t Au over 4.0 meters in Lynx Corridor. Mineralization contains 1% pyrite clusters and trace pyrite-silica flooding within a moderate chlorite and weak silica altered rhyolite.

OSK-W-18-1424 intersected 4.24 g/t Au over 2.5 metres in Lynx 4. Mineralization contains up to 2% pyrite-tourmaline and 1% pyrite in quartz-carbonate veins within a sericitized zone at the contact between a porphyritic felsic dike and a rhyolite.

OSK-W-18-1432-W1 intersected 8.89 g/t Au over 2.5 metres in Lynx 4. Mineralization contains up to 15% pyrite stringers at low core angles, 2% disseminated pyrite and traces of pyrite in ptygmatic tourmaline veins at the contact between a sericitized porphyritic felsic dike and a strongly bleached gabbro.

OSK-W-18-1443 intersected 4.25 g/t Au over 2.0 metres in Lynx HW. Mineralization contains 10% disseminated pyrite and trace pyrite clusters within a bleached, chloritized and silicified gabbro.

OSK-W-18-1450 intersected 36.7 g/t Au over 2.2 metres in Lynx 2. Mineralization contains up to 8% pyrite-silica flooding within a strong silica and weak sericite altered gabbro.

OSK-W-18-1454 intersected 17.0 g/t Au over 2.6 metres in Lynx 4. Mineralization is composed of 2% disseminated pyrite and quartz-tourmaline veins, and 1% pyrite-tourmaline stringers within a strong sericite altered rhyolite.

OSK-W-18-1455 intersected 4.12 g/t Au over 2.0 metres in Lynx HW. Mineralization contains up to 4% disseminated pyrite, up to 2% pyrite stringers and trace pyrite clusters at the contact between a fuchsite altered gabbro and a felsic porphyritic dike.

OSK-W-18-1460 intersected 4.50 g/t Au over 5.4 metres in Lynx HW. Mineralization contains 2% pyrite-silica flooding and 1% disseminated pyrite at the contact between a strong silica altered rhyolite and a felsic intrusion.

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  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 as of December 31, 2017.