A facile one-step solution-phase route to RGO/Ni3S2 on nickel foam (RGO/Ni3S2/NF) was presented. The RGO/Ni3S2/NF (RNS) nanocomposites were hydrothermal-assisted synthesized, in which nickel foam acted as an auxiliary reductant of GO and S, a Ni source of Ni3S2, and a substrate for composite film. RGO/Ni3S2/NF composites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The electrochemical performances of the supercapacitor with as-synthesized RGO/Ni3S2/NF (RNS) electrodes are evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 2M KOH aqueous solution. It is found that the RGO/Ni3S2/NF electrode exhibits superior supercapacitor performance (7440 mF cm−2 at 10mAcm−2, i.e., 2188.8 F g−1 at 2.9 A g−1), compared with the Ni3S2/NF electrode (4360 mF cm−2 at 10mAcm−2) and the RGO/Ni(OH)2/NF electrode (3400 mF cm−2 at 10mAcm−2) prepared under identical conditions. Both the temperature and sulfur content play important roles in the controlled synthesis of RNS and its electrochemical performance.