Primero Mining : Provides Exploration Update; Black Fox Deep Central Zone Expanded to the West; Vein Extensions at San Dimas and Promising Lechuguilla Concession Results

PRIMERO PROVIDES EXPLORATION UPDATE;

BLACK FOX DEEP CENTRAL ZONE EXPANDED TO THE WEST; VEIN EXTENSIONS AT SAN DIMAS AND PROMISING LECHUGUILLA CONCESSION RESULTS

Toronto, Ontario, September 19, 2016 --- Primero Mining Corp. ("Primero" or the "Company") (TSX:P, NYSE:PPP) today announced the results of successful exploration at the Company's Black Fox mine located near Timmins, Ontario, Canada and the San Dimas mine located in Durango, Mexico.

Black Fox Highlights:

• Deep Central Zone Positive Production Results: Initial mining of the Black Fox Deep Central Zone has delivered positive production results with long-hole stoping producing 3,885 tonnes grading 8.3 g/t gold to-date. Development in ore has produced an additional 4,350 tonnes grading 10.9 g/t gold. Delineation drilling continues to confirm the high-grade tenure of the Deep Central Zone with drill hole 520-EX346-06 intercepting 27.9 g/t gold over 5.8 metres at 800 metres depth.

• Mineralization Identified West of Deep Central Zone: Recent exploration drilling west of the Black Fox Deep Central Zone returned positive results with significant gold grades including 28.1 grams per tonne ("g/t") gold over 2.7 metres (520-EX286-05), 4.6 g/t gold over 5.4 metres (520-EX286-01) and 9.1 g/t gold over 1.2 metres (520-EX286-02).

  San Dimas Highlights:

• High-Grade Victoria Vein Extended: Exploration drilling at San Dimas continues to target the north- eastern extension of the Victoria vein, returning positive results including 208.7 g/t gold and 3,037 g/t silver over 1.3 metres true width (VIC16_379), 11.5 g/t gold and 590 g/t silver over 3.5 metres true width (VIC16_374), and 12.6 g/t gold and 817g/t silver over 2.3 metres true width (VIC16_378).

• Discovery of High Grade at Surface on Lechuguilla Concession: Exploration of the Causitas vein, located on the 30,192 hectare Lechuguilla concession near the main road between Durango and Tayoltita, has been traced at surface over 200 metres of strike length with true widths of up to 6 metres. Highlights of channel sampling include 7.1 g/t gold equivalent over 4.5 metres true width including 10.9 g/t gold equivalent over 2.0 metres true width (L-05), and 5.0 g/t gold equivalent over 3.0 metres true width including 9.8 g/t gold equivalent over 1.2 metres true width (L-02).

• Other Veins Identified in Causitas "Window": Following the initial success at the Causitas vein, Primero has been investigating nearby outcroppings within the Causitas "geological window", this being the area where erosion has exposed the lower volcanic sequence containing mineralized veins. The Causitas "window" is much more extensive in area than originally indicated and to date Primero has identified 2 other veins located within close proximity and near the main road.

"I am exceptionally pleased with the results achieved by our Black Fox and San Dimas exploration teams," stated Ernest Mast, President and Chief Executive Officer. "At Black Fox, the Deep Central Zone is now delivering production ore and we have successfully identified additional high-grade mineralization to the west. At San Dimas, it is reassuring to see that our high-grade veins can continue to be extended with similar or greater widths than currently being mined. And as we look regionally at San Dimas, onto our concession not covered by the Silver Purchase Agreement I am optimistic about the initial results from the Causitas vein which has the potential to augment current mill feed given its proximity to an existing main road. The Causitas area, located in the Lechuguilla concession, is highly prospective and I look forward to announcing additional exploration results from a drilling program from this area before year-end."

BLACK FOX - CANADA

Deep Central Zone Delivers Positive Production Results

The discovery, delineation and now commencing production from the Black Fox Deep Central Zone is an important milestone for the mine. When Primero acquired the Black Fox mine only two exploration holes had been drilled into the area, and over the past few years, Primero has successfully expanded, delineated, and mined a ramp to access the Deep Central Zone. Current reserves, as at December 31, 2015, totalled 0.6 million tonnes of probable reserves grading 6.2 g/t gold and containing 116,000 ounces.

Following ramp construction completed in early 2016, Primero has developed mining levels on the 640, 660, and 680 metre levels ahead of initial long-hole production. Primero has now achieved initial production mining of the Deep Central Zone, which has returned positive results with grades and tonnes reconciling well with the production block model. First long-hole production blasting occurred in early-September, and to-date 3,885 production tonnes have been recovered from stoping between the 640 and 660 metre levels with an average grade of 8.3 g/t gold. Long-hole production will continue to ramp-up from this area with underground production expected to average 800 tonnes per day in Q4 2016.

Development in ore is underway on the 680 level ahead of long-hole stoping production between the 660 and 680 levels. Currently, 91 metres of lateral development have been completed containing 4,350 tonnes of ore with an average grade of 10.9 g/t gold in muck samples (cut at 30 g/t).

Further at depth, recent exploration drilling has reconfirmed the high-grade tenure of the Deep Central Zone with drill hole 520-EX346-06 intercepting 27.9 g/t gold over 5.8 metres at approximately 800 metres depth. Deep drilling efforts remain ongoing and results from 800 to 1,000 metres depth are expected before year- end.

Details from hole 520-EX346-06 are shown in Table 1 below with intercept location identified in Figure 1.

Table 1: Black Fox Deep Central Zone - Highlighted Exploration Drilling Results

Deep Central Zone Extended to the West

After successfully expanding and delineating the Black Fox Deep Central Zone, Primero has shifted focus to other priority target areas located to the west and at depth. Recent exploration of the west targets has returned positive results with significant gold grades including 28.1 g/t gold over 2.7 metres (520-EX286- 05), 4.6 g/t gold over 5.4 metres (520-EX286-01) and 9.1 g/t gold over 1.2 metres (520-EX286-02).

Drill hole 520-EX286-05 was drilled to test an extension of the W1 High Quartz target, which remains open at depth. Holes 520-EX286-01 and -02 have identified the W5 Far West target which requires further infill exploration and remains open at depth.

Highlighted drill results from the deep west targets are shown in Table 2 with intercept locations identified in Figure 1.

Table 2: Black Fox Deep West Targets - Highlighted Exploration Drilling Results

Three underground diamond drill rigs are now active on the 520 level exploration drift and will continue to target mineralization located down-plunge and to the west of the Black Fox Deep Central Zone. In addition, two surface drill rigs continue to test for other areas of Froome-like mineralization.

SAN DIMAS - MEXICO

High-Grade Victoria Vein Extended

As described in early 2016, Primero has assembled a new structural model for the Victoria vein based on new information received from drilling completed in 2015. This model includes a detailed interpretation of the principal and secondary faults that displace the vein principally along strike. A combination of the structural and geochemical characterizations has allowed the exploration team to better understand the plunge of the ore zone and to identify a possible extension of the known mineralization to the northeast of the vein.

Follow-up exploration drilling has continued to build on the positive results released in February 2016 (refer to Primero's news release dated February 29, 2016) and has extended the high-grade mineralization further to the northeast. Highlighted results from this step-out drilling include 208.7 g/t gold and 3,037 g/t silver over

1.3 metres true width (VIC16_379), 11.5 g/t gold and 590 g/t silver over 3.5 metres true width (VIC16_374), and 12.6 g/t gold and 817 g/t silver over 2.3 metres true width (VIC16_378). The Company

plans to commence delineation drilling of this new area before the end of September. The Victoria vein continues to remain open to the northeast.

Highlighted drill results from the Victoria vein are shown in Table 3 with locations identified in Figure 2.

Table 3: San Dimas Victoria Vein - Highlighted Drilling Results

Economic Mineralization Discovered in Extended Lechuguilla Concession

Following positive grab samples reported in early-August, Primero has undertaken a program of channel sampling and detailed mapping of the Causitas vein located on the large-scale Lechuguilla concession approximately 18 kilometres south of the San Dimas mill. The vein has been outlined at surface over 200 metres of strike length with true widths of up to 6 metres. The vein is located close to the main road running between Tayoltita and Durango.

Highlights from the recent Causitas vein channel sampling include 7.1 g/t gold equivalent (''AuEq'') over 4.5 metres true width including 10.9 g/t AuEq over 2.0 metres true width (L-05), and 5.0 g/t AuEq over 3.0 metres true width including 9.8 g/t AuEq over 1.2 metres true width (L-02).

Channel sample results from the Causitas vein are shown in Table 4 with locations identified in Figure 4.

Primero's geologists are still working to improve their preliminary interpretation of the Causitas vein, but the initial results show a regular distribution of gold and silver values along the vein. The vein is located near the surface contact between the lower volcanic and upper volcanic groups. This observation suggests that erosion in the Causitas area was less extensive and infers that the exposed vein at surface is near the top of the ''favourable horizon'', where the precious metals deposits form. To test the Causitas vein at depth, Primero will be mobilizing a drill rig expected to be on-location at the Causitas vein in October 2016.

Following the initial success at the Causitas vein, Primero has been investigating nearby outcroppings within the nearly-unexplored Causitas ''geological window'', this being the area where erosion has exposed the lower volcanic sequence containing mineralized veins. The Causitas ''window'' is much more extensive in area than originally indicated and to date Primero has identified 2 other veins located within close proximity. The Los Pajaritos vein located 1.0 kilometre to the northwest and the El Tablon vein located 3.8 kilometres to the southeast. Primero's geologists have identified other minor structures and alteration within the area which will be subject to more detailed exploration.