Reduced graphene oxide (rGO) and NiO composites were prepared with an environmentally friendly method, in which hydrogen gas was employed as the reducing agent to convert reduced graphene oxides. Our study indicates that the success of this new approach is because NiO not only is an additive of the composites but also acts as a catalyst to facilitate the reduction. Characterization with scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction illustrates that the as-prepared rGO/NiO composites have a three-dimensional flowerlike hierarchical structure, which prevents graphene from taking face to face aggregation and therefore greatly improves the stability of the composite materials. A hybrid capacitor electrode made of the NiO/rGO composites shows great performance, in which the maximum specific capacitance is close to 428 F g(-1) at a discharge current density of 0.38 A g(-1) in a 6.0 M KOH electrolyte.