Assays Demonstrate Strong Continuity in A3 Shear and Along Strike at the Arrow Deposit

Assays Demonstrate Strong Continuity in A3 Shear and Along Strike at

the Arrow Deposit

Vancouver, BC, December 11, 2017 – NexGen Energy Lt d. (“NexGen” or the “Company”) (TSX:NXE, NYSE

MKT:NXE) is pleased to report assay results for 21 holes from Arrow as part of our recently concluded summer

drilling program on our 100% owned, Rook I property, in the Athabasca Basin, Saskatchewan.

Arrow Highlights:

A3 Infill Drilling

• AR-17-147c3 intersected 60.0 m at 3.70% U 3O8 (597.5 to 657.5 m) including 33.0 m at 6.51% U 3O8

(607.0 to 640.0 m) and 6.0 m at 17.68% U 3O8 (634.0 to 640.0 m). This is the best assay to date at the

Arrow Deposit in the A3 Shear.

• AR-17-155c2 intersected 18.5 m at 4.32% U 3O8 (560.5 to 579.0 m) including 7.0 m at 11.23% U 3O8

(562.0 to 569.0 m) in the A3 shear.

• AR-17-147c2 intersected 28.5 m at 1.74% U 3O8 (604.0 to 632.5 m) including 5.5 m at 8.56% U 3O8

(605.0 to 610.5 m) in the A3 shear.

Step-Out Drilling

Assays from step-out drilling in both the Southwest and Northeast ‘Gaps’ confirms mineralization is now known

to be continuous in both of these resource expansion areas.

Southwest Gap Step-Outs

• AR-17-156c1 intersected 32.5 m at 1.04% U 3O8 (670.5 to 703.0 m) including 9.0 m at 2.72% U 3O8

(676.5 to 685.5 m) in the Southwest Gap.

Northeast Gap Step-Outs

• AR-17-129c5 intersected 3.5 m at 3.37% U 3O8 (757.5 to 761.0 m) and 8.0 m at 1.54% U 3O8 (766.0 to

774.0 m) and 23.5 m at 0.97% U 3O8 (851.5 to 875.0 m) in the Northeast Gap.

• AR-17-129c7 intersected 13.0 m at 1.63% U 3O8 (783.0 to 796.0 m) including 5.5 m at 3.80% U 3O8

(783.0 to 788.5 m) in the Northeast Gap.

Drill hole locations and long sections are shown in Figures 1 to 3.

Development, Activities & Financial

• Assay results for 28 holes at the Arrow Deposit and 31 holes from South Arrow remain pending.

• Multiple advanced-stage technical studies including geotechnical work, hydrogeological work, and

metallurgy continue in advance of the maiden Pre-Fe asibility Study scheduled to be published in

Q3/2018.

• Planning for winter 2018 development and exploration program is advanced.

• The Company has cash on hand of approximately $165 million.

Garrett Ainsworth, Vice-President, Exploration and Development, commented: “These Arrow drill assays a re

impressive results for both the A3 High Grade Domain infill and resource expansion areas in the Southwest and

Northeast Gaps. The A3 High Grade Domain is develop ing very nicely and the continuation of mineralizat ion

along both strike directions continues to show sign ificant drilling is required to determine the exten t of the

mineralized Arrow footprint. ”

Leigh Curyer, Chief Executive Officer, commented: “Arrow’s growth continues. Together, the project

development studies are advancing for the release of a Pre-Feasibility Study scheduled for Q3 2018. The project

development team has recently expanded with the app ointment of high calibre industry professionals

reflecting the nature of the Arrow Project as a uni que opportunity to contribute to this generational mineral

resource. The Company is well positioned to enter 2 018 and looking forward to delivering the next stag es of

exploration growth and project development.”

Figure 1: A3 Shear Mineralized Long Section

Figure 2: Arrow Deposit Schematic Long Section

Figure 3: Arrow Drill Hole Locations

Table 1: Arrow Deposit Assay Results

Drill Hole

Athabasca Group -

Basement

Unconformity Depth

(m)

SRC Geoanalytical Results

Hole ID Azimuth Dip

Total

Depth

(m)

From (m) To (m) Interval

(m) U3O8 (wt%)

AR-17-129c5 327 -70 960.50 N/A 616.00 617.00 1.00 0.11

655.00 657.50 2.50 0.12

692.50 693.00 0.50 4.00

728.50 730.00 1.50 0.14

740.00 740.50 0.50 0.46

748.50 751.50 3.00 0.40

754.00 754.50 0.50 0.36

757.50 761.00 3.50 3.37

766.00 774.00 8.00 1.54

777.50 781.00 3.50 1.79

784.50 804.50 20.00 0.07

810.00 814.50 4.50 0.05

851.50 875.00 23.50 0.97

878.50 879.00 0.50 0.07

882.00 892.00 10.00 0.15

901.50 902.00 0.50 0.06

911.00 911.50 0.50 0.04

AR-17-129c6 327 -70 876.50 N/A 595.00 595.50 0.50 0.05

710.50 711.00 0.50 0.06

735.50 736.00 0.50 0.02

778.00 778.50 0.50 0.02

817.00 817.50 0.50 0.02

AR-17-129c7 327 -70 960.50 N/A 649.50 650.50 1.00 0.05

668.00 669.50 1.50 0.06

676.00 678.50 2.50 0.40

704.50 705.50 1.00 0.24

731.00 731.50 0.50 3.02

736.00 736.50 0.50 0.04

765.50 766.00 0.50 0.01

783.00 796.00 13.00 1.63

incl. 783.00 788.50 5.50 3.80

804.00 819.50 15.50 0.04

829.50 831.00 1.50 0.10

856.50 857.00 0.50 0.07

906.00 906.50 0.50 0.04

AR-17-143c2 147 -70 729.50 N/A 558.00 558.50 0.50 0.03

561.50 563.00 1.50 0.11

AR-17-143c3 147 -70 974.00 N/A 662.00 664.00 2.00 0.09

667.00 673.00 6.00 0.21

677.00 677.50 0.50 0.06

682.00 704.50 22.50 0.17

incl. 689.50 697.50 8.00 0.36

712.50 713.50 1.00 0.11

742.50 743.00 0.50 0.15

772.50 773.00 0.50 0.18

813.00 813.50 0.50 0.03

855.00 860.00 5.00 0.02

863.50 868.50 5.00 0.04

885.50 886.50 1.00 0.03

924.00 928.00 4.00 0.82

930.50 934.00 3.50 3.45

938.00 938.50 0.50 0.27

AR-17-146c1 327 -70 910.50 110.40 630.50 631.50 1.00 0.37

686.00 688.00 2.00 0.73

691.00 695.00 4.00 0.33

697.50 703.00 5.50 0.07

705.50 709.50 4.00 0.38

721.50 744.00 22.50 0.07

748.00 749.00 1.00 0.03

754.00 755.50 1.50 0.21

765.50 768.50 3.00 0.07

795.50 797.00 1.50 0.05

AR-17-146c2 327 -70 907.00 N/A 661.50 663.00 1.50 1.15

682.50 683.00 0.50 0.03

685.50 688.00 2.50 0.02

694.50 696.00 1.50 0.74

698.50 699.00 0.50 0.04

704.50 705.50 1.00 1.79

737.00 738.00 1.00 0.06

742.00 749.00 7.00 0.05

752.00 772.50 20.50 0.48

incl. 752.00 763.50 11.50 0.79

777.00 778.00 1.00 2.65

780.50 782.50 2.00 4.77

AR-17-146c3 327 -70 993.50 N/A 676.50 677.50 1.00 0.04

709.00 709.50 0.50 0.29

722.50 723.50 1.00 0.48

728.00 732.50 4.50 0.12

744.00 745.00 1.00 0.24

753.00 772.50 19.50 0.26

incl. 753.00 763.00 10.00 0.46

777.00 777.50 0.50 0.03

783.50 784.00 0.50 0.05

789.00 826.50 37.50 0.15

Incl. 789.00 798.50 9.50 0.29

912.50 913.00 0.50 0.09

946.00 947.00 1.00 0.07

952.00 956.00 4.00 0.03

963.50 964.50 1.00 0.08

AR-17-147c1 327 -70 621.50 133.90 454.00 454.50 0.50 0.19

492.50 495.50 3.00 2.24

510.00 511.00 1.00 0.81

515.00 515.50 0.50 0.11

521.00 525.00 4.00 0.95

532.50 536.50 4.00 0.32

541.50 545.00 3.50 0.33

556.50 567.50 11.00 2.25

incl. 557.00 558.00 1.00 21.20

572.00 572.50 0.50 0.87

576.00 592.00 16.00 1.31

incl. 580.50 582.50 2.00 7.63

598.50 600.00 1.50 0.02

606.00 608.00 2.00 0.09

AR-17-147c2 327 -70 660.50 133.90 454.50 455.00 0.50 0.11

498.00 499.50 1.50 0.71

529.50 530.50 1.00 0.42

534.00 534.50 0.50 0.66

544.50 550.50 6.00 0.49

556.00 556.50 0.50 0.02

560.00 569.00 9.00 0.70

580.50 581.50 1.00 0.05

587.00 587.50 0.50 0.06

590.00 593.00 3.00 0.04

604.00 632.50 28.50 1.74

incl. 605.00 610.50 5.50 8.56

AR-17-147c3 327 -70 682.50 133.90 454.50 455.50 1.00 0.06

499.50 502.00 2.50 0.34

515.50 517.00 1.50 0.05

528.50 529.50 1.00 0.49