NiS2/graphene composite is synthesized by a facile hydrothermal reaction between NiCl2 and l-cysteine in the presence of graphene oxide sheets. l-Cysteine serves as both the sulfur source for NiS2 and reductant for reduction of graphene oxide sheets. The reduced graphene oxides can be used as a platform for growth of NiS2 particles and restrain NiS2 from agglomerating during hydrothermal process. The results of characterizations show that the sphere-like NiS2 particles exhibit smaller sizes and are well dispersed on the surface of reduced graphene sheets. The electrochemical measurements demonstrate that the NiS2/graphene composite delivers a reversible capacity as high as 1200 mAh g−1 at a current density of 100 mA g−1 and enhanced high-rate capability of 740 mAh g−1 at a high current density of 1000 mA g−1. After 1000 cycles, the NiS2/graphene still preserves the reversible capacity about 810 mAh g−1 at a current density of 500 mA g−1, indicating its excellent cyclic stability.