A reduced graphene modified Ta2O5 photocatalyst (Ta2O5–rG) was prepared using a one-step hydrothermal method, and the photocatalytic reduction of an aqueous CO2 solution to CH3OH and H2 using the NiOx–Ta2O5–rG photocatalyst was performed. Due to graphene's electron transfer and collecting characteristics, reduced graphene was found to be important in achieving high methanol yields for this multi-electron reduction process. The NiOx–Ta2O5–rG photocatalyst also showed good production selectivity for the competing reactions of CH3OH and H2 generation in aqueous CO2 or CO2/NaHCO3 solution.