A facile one-pot impregnation-thermal reduction strategy was employed to fabricate sandwich-like graphene-g-C3N4 (GCN) nanocomposites using urea and graphene oxide as precursors. The GCN sample exhibited a slight red shift of the absorption band edge attributed to the formation of a C-O-C bond as a covalent cross linker between graphene and g-C3N4. The GCN sample demonstrated high visible-light photoactivity towards CO2 reduction under ambient conditions, exhibiting a 2.3-fold enhancement over pure g-C3N4. This was ascribed to the inhibition of electron-hole pair recombination by graphene, which increased the charge transfer.