Osisko Intersects 61.8 g/t Au Over 2.5 Metres At Lynx

Lynx 4 Extended 235 Metres to NE

(Toronto, October 12, 2017)  Osisko Mining Inc. (OSK:TSX. “Osisko” or the “Corporation”) is pleased to provide new results from the ongoing drill program at its 100% owned Windfall Lake gold project located in Urban Township, Abitibi, 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 11 drill holes focused on infill and expansion drilling in the Lynx deposit are presented below.

Highlights from the new results include: 61.8 g/t Au over 2.5 metres in OSK-W-17-953; 21.2 g/t Au over 4.3 metres in OSK-W-17-1169; 16.9 g/t Au over 4.0 metres in OSK-W-17-1190; and 29.8 g/t Au over 2.0 metres in OSK-W-17-881. 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: FW = Foot Wall; VNCR = crustiform vein.

OSK-W-17-856 intersected Lynx 2 returning 5.03 g/t Au over 5.6 metres (including 13.1 g/t Au over 0.6 metres and 15.2 g/t Au over 1.0 metre). Mineralization includes up to 18% pyrite, 5% quartz-carbonate veins and ptygmatic tourmaline veins related to rich silica bands.

OSK-W-17-881 intersected two intervals: 6.54 g/t Au over 4.2 metres (including 15.1 g/t Au over 1.4 metres) and 29.8 g/t Au over 2.0 metres (including 59.4 g/t Au over 1.0 metre). Both intervals are related to Lynx 2 Footwall at the contacts between a rhyolite and a gabbro. Mineralization is composed of up to 1% pyrite stringers and quartz-tourmaline veins within sericite and fuchsite alteration.

OSK-W-17-923 intersected 4.33 g/t Au over 3.0 metres in a strongly sericite and fuchsite altered gabbro. The mineralization is composed of up to 2% pyrite, 2% pyrite stringers and small crustiform veins. The interval correlates to the Lynx 4 corridor, extending the zone235 metres north-east of OSK-W-17-836 (116 g/t Au over 2.4 metres, uncut, previously reported May 23, 2017).

OSK-W-17-953 intersected Lynx 2 returning 61.8 g/t Au over 2.5 metres, uncut, (including 189 g/t Au over 0.8 metres) or 33.3 g/t Au over 2.5 metres cut. The mineralization is within a strongly silicified, sericitized and fuchsitized gabbro with 3% pyrite stringers, 2% disseminated pyrite and small crustiform veins.

OSK-W-17-998 intersected a crustiform vein returning 4.78 g/t Au over 4.5 metres between the Lynx 2 and Lynx 3 Zones. The vein contains up to 7% disseminated pyrite, 3% tourmaline and ptygmatic veins.

OSK-W-17-1003 intersected two intervals: 5.18 g/t Au over 2.6 metres (including 16.8 g/t Au over 0.8 metres) in Lynx 1 and 19.5 g/t over 2.0 metres (including 46.3 g/t Au over 0.8 metres) in Lynx 2. The first interval includes up to 5% pyrite clusters, 5% chalcopyrite and crustiform veins within a strongly sericitized gabbro. The second interval is at the contact between a gabbro and a strongly sericitized rhyolite. Fuchsite is also observed. The mineralization is composed of 10% pyrite stringers and few tourmaline ptygmatic veins.

OSK-W-17-1121 contains three intervals in crustiform veins: 19.0 g/t Au over 2.3 metres (including 58.8 g/t Au over 0.7 metres), 3.34 g/t Au over 2.1 metres and 8.62 g/t Au over 2.7 metres (including 13.7 g/t Au over 1.7 metres). The first is between Lynx 1 and Lynx 2 and the second and third are inside Lynx 3 Zone. All are hosted in a silica altered gabbro and mineralization is composed of up to 6% disseminated pyrite, up to 2% disseminated sphalerite and pyrite stringers.

OSK-W-17-1123 intersected 11.6 g/t Au over 2.1 metres (including 47.5 g/t Au over 0.4 metres) in Lynx 2. Mineralization is composed of 20% pyrite stringers within a strong silica alteration at the contact between a rhyolite and an andesite.

OSK-W-17-1128 intersected three intervals: 3.85 g/t Au over 5.5 metres in Lynx 3, 5.00 g/t Au over 2.0 metres in Lynx 2 and 14.0 g/t Au over 2.3 metres (including 25.7 g/t Au over 1.2 metres) in Lynx 6. The first interval is composed of up to 2% smoky quartz veins within a strongly silicified rhyolite, the second interval is within the gabbro and the third interval composed of up to 1% disseminated pyrite is at the contact between a felsic porphyritic intrusion and a gabbro.

OSK-W-17-1169 intersected two intervals 7.14 g/t Au over 2.4 metres (including 21.8 g/t Au over 0.4 metres) and 21.2 g/t Au over 4.3 metres (including 42.4 g/t Au over 1.0 metre). Both intervals correlate to Lynx 4. The first interval is a felsic porphyritic dike crosscutting the hosting rhyolite. The mineralization is composed of up to 15% pyrite stringers and pyrite-tourmaline stringers. The second interval is composed of semi-massive pyrite and trace of sphalerite hosted in a strongly silicified rhyolite.

OSK-W-17-1190 intersected two intervals: 11.0 g/t Au over 2.5 metres and 16.9 g/t Au over 4.0 metres (including 57.2 g/t Au over 0.7 metres). The mineralization in both intervals is composed of up to 10% disseminated pyrite and quartz-tourmaline veins. The first interval is within a strongly sericitized rhyolite, and the second interval is at the contact between a rhyolite and a felsic porphyritic dike. Both intersections correlate to the Lynx 4 corridor  300 meters up plunge of OSK-W-17-827 (57.0 g/t Au over 2.7 metres previously reported July 25, 2017).

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 dOr, 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-dOr 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.

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”, “managements 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 managements 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.

For further information please contact:
John Burzynski. President and Chief Executive Officer
Telephone: (416) 363-8653