WC-10%Co (mass fraction) nanocomposite was synthesized by high energy planetary ball milling at balls to powder mass ratio of 15. For inhibition of growth of WC grains during sintering, TaC and VC were used as inhibitors. Hardness and fracture toughness results reveal that the addition of TaC increases the toughness of hard metal and VC increases the hardness of the sample due to the effective reduction of WC grain size. The effect of co-addition of 0.6% TaC and 0.7% VC on physical and mechanical properties of WC-10%Co sintered sample was investigated. The hardness of the sample is increased to HV₃₀ 1 787, which is 24% more than that of the inhibitor-free sample; the fracture toughness achieves 8.7 MPa·m^1/2, 35% higer then that of the inhibitor-free sample; the grain growth is inhibited and grain size achieves 0.38 μm.