Nanocomposites of ZnO/CuO with rGO were synthesized using sonochemical and thermal treatment methods. The formation of ZnO and CuO phases on the rGO sheets and both ZnO/CuO in the ternary component nanocomposites were confirmed from IR spectroscopy and X-ray photoelectron spectroscopy. The microstructure of the nanocomposites as revealed by TEM and FE-SEM suggested that CuO was decorated as nano-rods, whereas ZnO particles retained the spherical shape. In case of ternary nanocomposite, both nano-rods and spherical particles were agglomerated on the rGO sheets. The pseudocapacitive behavior of ZnO-rGO nanocomposite corresponded to relatively higher specific capacitance (344.6 F/g) compared with other nanocomposites. The galvanostatic cyclic charge/discharge (GCD) tests also confirmed that ZnO-rGO nanocomposite could provide the highest specific energy (21.7 Wh/kg) and power density (129.8 kW/kg) at 0.4 A/g compared with CuO-rGO and ZnO/CuO-rGO.