A hierarchical electrode structure, consisting of cobalt oxide and nitrogen-doped graphene foam (NGF), has been fabricated with the aim of achieving enhanced charge-storage performance. Characterization of the material via electron microscopy and Raman spectroscopy demonstrates that the Co3O4 nanosheets grow vertically on NGF and the nanosheets are mesoporous with pore diameters between 3 and 8 nm. The Co3O4/NGF electrode shows an enhanced charge-storage performance, attributed to the 3D hierarchical structure and the synergistic effect of Co3O4 and NGF. The present study shows that specific capacitances as high as 451 F g(-1) can be obtained, indicating that high-performance electrochemical capacitors can be made using electrode materials with advanced structures. The present electrode design can be readily extended to other electroactive materials and their composites.