A green and facile approach was used for the synthesis of a graphene nanosheet NiO composite. Using glucose as the green reduction agent, graphene oxide was reduced to graphene and formed a membrane-like NiO–GNS–GC composite via a hydrothermal method. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, the electrochemical performance of the composite was evaluated by cyclic voltammetry and galvanostatic charge–discharge. The obtained NiO–GNS–GC composite exhibits the highest specific supercapacitance of 1495 F g⁻¹ at a current density of 0.5 A g⁻¹ in 6 M KOH, which is much higher than that of pure NiO (478 F g⁻¹) and pure GNS (92 F g⁻¹) along with 90% specific capacitance remaining after 1000 cycles. This could be attributed to the layered sandwich nanostructure and the fact that during the hydrothermal process glucose transformed to a kind of amorphous carbon which, as a spacer, could stabilize the structure of the as-prepared GNS.