Co₃O₄/RGO composites with Co₃O₄ porous nanosheets attached on reduced graphene oxide (RGO) sheet were fabricated through a facile refluxing method followed by a thermal annealing process. Pores with sizes of several nanometers are uniformly distributed in Co₃O₄ nanosheets. The composites as electrode materials for supercapacitors were investigated. They deliver a specific capacitance as high as 518.8 F g⁻¹ at the current density of 0.5 A g⁻¹, and great cycling stability with a decay of about 7.6% after 1500 continuous charge–discharge cycles at the current density of 10 A g⁻¹. The excellent capacitive performance can be attributed to the excellent electrical properties, large surface area and well-connected conductive network derived from the structural advantages of the Co₃O₄ porous nanosheets and RGO support. The facile synthesis and the excellent capacitive performance make the Co₃O₄/RGO composites a promising candidate for electrode materials in electrochemical energy storage systems.