Various gold-supported TiO2 catalysts (0.5-3.0 wt.%) were prepared by a deposition-precipitation method, and their photocatalytic activity towards CO2 reduction was tested in the gas phase while using H2O as electron donor and UV and visible light as energy sources. CO and H2 are detected as major products in bare TiO2. However, the deposition of small Au nanoparticles (NPs) onto TiO2 was found to quantitatively enhance the reduction of CO2 mainly to methane and C2+ hydrocarbons. Transient absorption spectroscopy was used to correlate the improved CH4 production with an increased charge separation due to the electron transfer between the TiO2 and Au NPs. The amount of Au loaded onto TiO2 was optimized, with 1.0 wt.% showing the highest photocatalytic activity under UV light. Under visible irradiation, H2 and CH4 were identified as the main products, although showing significantly lower productions.