High-purity NiCo2S4 mesoporous nanosheets prepared through utilizing CS2 as novel sulfur source were fabricated as advanced electrode for electrochemical supercapacitors. Well-defined X-ray diffraction pattern, high specific surface areas and suitable pore size distribution (2∼6nm) were observed for the as-obtained NiCo2S4 sample, demonstrating remarkable electrochemical performances resulting from the porous feature of NiCo2S4 nanosheets that increase the amount of electroactive sites and facilitate the electrolyte penetration. The as-assembled asymmetric supercapacitor (ASC) exhibits a high energy density of 25.5Whkg−1 at a power density of 334Wkg−1 and still remains an impressive energy density of 10.8Whkg−1 at a high power density of 8kWkg−1. The outstanding performance of this ASC device will undoubtedly make the mesoporous NiCo2S4 nanosheets attractive for high-performance electrode materials.