Reduced graphene oxide (rGO)-wrapped octahedral Cu2O composites (GCCs) were successfully produced by an ultrasonication-assisted reduction of graphene oxide (GO) in the Cu2O precursor solution. During the ultrasound reaction, the reduction of GO and the growth of octahedral Cu2O crystals occurred simultaneously in conjunction with the deposition of Cu2O crystals on graphene. As a result of the introduction of rGO, the light absorption of octahedral Cu2O was markedly improved, the size of Cu2O crystals was decreased, and the self-aggregation of Cu2O crystals was effectively prevented. More importantly, the charge separation and transfer were effectively enhanced. Compared to the pure octahedral Cu2O crystals and commercial TiO2 (P25), the GCCs exhibited an increased degradation rate of methyl orange (MO) by 4.5 and 20.2 times, respectively. Meanwhile, upon the graphene loading, the photoelectric conversion efficiency of GCC electrodes was largely improved resulting in an efficiency of 0.151%, representing an 8 fold higher efficiency than that of pure Cu2O crystals.