Osisko Intersects 40.8 g/t Au Over 4.1 Metres at Windfall

President and CEO John Burzynski commented: "Good results again from our drilling at Windfall as we look forward to our initial mineral resource estimate on schedule for delivery in May. Although today's results are outside the cut-off date and won't be included in the mineral resource calculation in mid-March, they will add to the upside potential of Windfall as we head towards the feasibility study in early 2019. Particularly encouraging is that we are still seeing expansion potential in all of the main zones at Windfall-Lynx underscored in today's results with the extension of the Underdog FW4 Zone by 70 metres up plunge from the previous mineralized intercept."

OSK-EAG-12-424 intersected two intervals in FW3: 7.85 g/t Au over 2.4 metres and 10.0 g/t Au over 2.5 metres. The first interval is composed of up to 2% disseminated pyrite and 1% pyrite stringers at the contact between a chloritized andesite and a sericitized porphyritic dike. The second interval contains up to 2% pyrite and pyrite-tourmaline stringers within a strongly sericitized andesite with moderate fuchsite alteration.

OSK-W-16-706-W3 intersected FW2 returning 7.88 g/t Au over 2.2 metres in the Underdog Corridor. Mineralization is composed of 8% pyrite stringers within a moderately silicified and sericitized felsic porphyritic dike with weak fuchsite alteration.

OSK-W-17-943 new assay results extend the previously reported result of 4.51 g/t Au over 2.0 metres (March 2, 2018) to 3.25 g/t Au over 5.2 metres in Wolf HW. Mineralization is composed of 5% pyrite stringers, 2% disseminate pyrite within a sericitized and strongly silicified felsic porphyritic dike.

OSK-W-17-967 intersected two intervals in Caribou Extension: 23.2 g/t Au over 2.0 metres and 10.2 g/t Au over 4.5 metres. The first interval is composed of 2% pyrite stringers and disseminated pyrite within a strong sericite, weak silica altered rhyolite. The second interval is composed of 2% pyrite stringers, disseminated pyrite and quartz-tourmaline veins within a sericitized felsic porphyritic dike.

OSK-W-17-1139 intersected 4.44 g/t Au over 2.2 metres in FW3. Mineralization is composed of up to 2% pyrite stringers hosted in a sericitized felsic porphyritic dike.

OSK-W-17-1308-W1 intersected 7.27g/t Au over 2.0 metres in Wolf. Mineralization is composed of trace pyrite stringers and disseminated in moderately chloritized and sericitized felsic porphyritic dike.

OSK-W-17-1336-W1 intersected 6.12 g/t Au over 7.5 metres in FW3. Mineralization is composed of up to 5% pyrite clusters, 1% pyrite stringers and a 20 centimetres zone with 15% ptygmatic tourmaline veins hosted in a sericitized and silicified felsic porphyritic dike.

OSK-W-17-1352 intersected 9.39 g/t Au over 2.0 metres in Caribou Extension. Mineralization is composed of up to 8% tourmaline-pyrite stringers at the contact between a gabbro and a felsic intrusive unit with weak fuchsite alteration.

OSK-W-17-1368 intersected 3.77 g/t Au over 2.0 metres and 8.05 g/t Au over 2.1 metres in Caribou Extension. The first interval is composed of trace pyrite in stringers and disseminated within a weak sericite and silica altered felsic porphyritic dike. The second interval is composed of 2% pyrite stringers, 5% pyrite-tourmaline stringers, 3% ptygmatic tourmaline veins within a sericitized and silicified rhyolite.

OSK-W-17-1369 intersected 5.67 g/t Au over 6.3 metres in Caribou. Mineralization is composed of up to 7% pyrite stringers and 10% disseminated pyrite in an alternation of mafic and felsic volcanic units.

OSK-W-17-1371 intersected 3.19 g/t Au over 2.0 metres in Caribou Extension. Mineralization is composed of disseminated pyrite and pyrite in quartz-tourmaline veins within a sericitized rhyolite.

OSK-W-17-1378 intersected 4.03 g/t Au over 2.0 metres in Zone 27 and 9.26 g/t Au over 2.3 metres in a vein. The first interval is composed of 5% pyrite within a felsic porphyritic dike. The second interval is composed of quartz-carbonate vein with local visible gold hosted in the Red Dog intrusion.

OSK-W-17-1402 intersected 5.38 g/t Au over 5.0 metres, 4.09 g/t Au over 2.0 metres and 4.99 g/t Au over 2.0 metres in FW3. All three mineralized intervals are composed of up to 1% pyrite-silica flooding and trace pyrite stringers within a sericitized felsic porphyritic dike.

OSK-W-18-762-W1 intersected 11.1 g /t Au over 2.0 metres in FW4. Mineralization is composed of 2% pyrite stringers, 1% pyrite-tourmaline stringers and 30 centimetres of strong pyrite silica flooding within a sericitized and silicified felsic porphyritic dike.

OSK-W-18-823-W2 intersected two intervals in FW1: 11.7 g/t Au over 2.3 metre and 40.8 g/t Au over 4.1 metres. The first interval is composed of a pyrite-tourmaline stringer with 20% pyrite and local visible gold. Mineralization is in strong pervasive silica flooding and calcite alteration within a sericitized felsic porphyritic dike. The second interval is composed of up 2% pyrite stringers, trace pyrite-tourmaline stringer, disseminated pyrite, chalcopyrite and local visible gold within a moderate sericite altered, fragmental, felsic porphyritic dike.

OSK-W-18-1402-W1 intersected four intervals: 3.52 g/t Au over 2.0 metres and 53.9 g/t Au over 2.9 metres in FW1, 6.63 g/t Au over 2.6 metres in FW3 and 4.47 g/t Au over 2.4 metres in FW4. In the first and second intervals, mineralization is composed of local visible gold, up to 15% pyrite and tourmaline ptygmatic veins within a strongly sericitized and silicified felsic porphyritic dike. The third interval is composed local visible gold, 2% pyrite stringers, 1% pyrite stockwork and 2% pyrite-silica flooding. FW3 mineralisation is hosted in sericitized and silicified felsic porphyritic dike. The last interval is composed of 5% disseminated pyrite and 3% pyrite in smoky quartz veins within a porphyritic felsic dike with weak sericite alteration and moderate silica alteration.

OSK-W-18-1421 intersected 36.1 g/t Au over 3.2 metres in FW4. Mineralization is composed of local visible gold and up to 20% pyrite stringers with pervasive silica flooding in a felsic fragmental intrusion. The interval extends FW4 70 metres up plunge of OSK-W-16-735 (33.6 g/t Au over 4.2 metres, previously reported November 8, 2016).

OSK-W-18-1431 intersected two intervals: 3.57 g/t Au over 2.0 metres in FW2 and 13.5 g/t Au over 2.8 metres FW3. The first interval is composed of up to 8% semi-massive pyrite and 1% pyrite clusters within in a moderately silicified felsic porphyritic dike. The second interval is composed of up to 30% semi-massive pyrite within a sericite and silica altered felsic porphyritic dike.

OSK-W-18-1435 intersected 32.8 g/t Au over 2.3 metres in Bobcat. Mineralization is composed of 15% disseminated pyrite, ptygmatic tourmaline veins and pervasive silica flooding within a silicified and sericitized felsic porphyritic dike.

OSK-W-17-1441 intersected 3.41 g/t Au over 2.8 metres in Bobcat. Mineralization is composed of up to 10% semi-massive pyrite, 3% pyrite-tourmaline stingers within a strongly sericitized rhyolite.

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 ("NI 43-101").

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 as of December 31, 2017.

Cautionary Note Regarding Forward-Looking Information

This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. The information in this news release about the Windfall Lake gold deposit being one of the highest grade resource-stage gold projects in Canada; the current 800,000 metre drill program; the significance of new results from the ongoing drill program at the Windfall Lake gold project; the significance of assay results presented in this press release; the type of drilling included in the drill program (definition drilling, expansion drilling to the NE of the main deposit and adjacent Lynx deposit, and exploration drilling on the greater deposit and Urban-Barry project area); potential mineralization; the potential to extend mineralization up and down-plunge and at depth at the Windfall Lake gold deposit; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information". Any statement that involves discussions with respect to predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. This forward-looking information is based on reasonable assumptions and estimates of management of the Corporation. at the time it was made, involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Osisko to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information.
Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management's geological modelling; the ability of Osisko to complete further exploration activities, including drilling; property interests in the Windfall Lake gold project; the ability of the Corporation to obtain required approvals and complete transactions on terms announced; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions. Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information, Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.