The effect of graphene-nanosheets (GNs) on the mechanical properties and microstructure of the S390 HSS alloy was investigated. The S390 HSS sample reinforced with 0.25, 0.5, and 0.75 wt.% GNS. Powder metallurgy technique was used to prepare all samples. The elemental powders of the alloy were milled in a planetary ball mill by 10:1 ball to powder ratio with speed 350 rpm for 48 hours, and the mixed powders were warm compacted by the uni-axial press at 550 ⁰ C under 500 MPa and then sintered in a vacuum furnace at 1370 • C for 1 hour. X-ray diffraction shows the formation of secondary carbide phases and martensite. The density result indicates the decreasing of density values by GNS additions. The mechanical properties show an increase in the hardness and wear resistance by increasing the graphene content. The specimens are metallographically examining using Scanning Electron Microscopy (SEM), and also the electron backscatter diffraction shows a good distribution of GNS in the HSS matrix.