A facile and efficient strategy for preparing reduced graphene oxide–cobalt molybdate (RGO/CoMoO4) nanocomposites assisted by microwave irradiation for the first time is demonstrated. The resulting nanocomposites are comprised of CoMoO4 nanoparticles that are well-anchored on graphene sheets by in situ reducing. The prepared RGO/CoMoO4 nanocomposites have been thoroughly characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. Importantly, the prepared nanocomposites exhibit excellent electrochemical performance for supercapacitors. Results show that RGO/CoMoO4 nanocomposites exhibited much better electrochemical capability than pure-CoMoO4 and RGO/CoMoO4 for annealing. RGO/CoMoO4 nanocomposites with 37.4wt% CoMoO4 content achieved a specific capacitance about 322.5Fg−1 calculated from the CV plots at 5mVs−1, which was higher than that of pure-CoMoO4 (95.0Fg−1) and RGO/CoMoO4 for annealing (102.5Fg−1). The good electrochemical performance can be attributed to the synergistic effects of the individual components.