One-step microwave-assisted synthetic route for the fabrication of Mn3O4 nanoparticles@reduced graphene oxide (Mn3O4@rGO) nanocomposites has been demonstrated. The morphological structures of the nanocomposites are characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM), respectively. All of the results indicate that the microwave-assisted synthesis results in the growth of Mn3O4 and the reduction of graphene oxide simultaneously in ethylene glycol-water system. The specific capacitance of the as-prepared Mn3O4@rGO nanocomposite is higher than those of rGO and pure Mn3O4, which indicates the synergetic interaction between rGO and Mn3O4. The nanocomposites also have good rate capability and cycling stability in electrochemical experiments. This facile technique may be extended to the large scale and cost effective production of other composites based on graphene and metal oxide for many applications. (C) 2015 Elsevier Ltd. All rights reserved.