Photocatalytic thin films on quartz substrates were simply prepared by spraying a sol of copper metal (Cu)-doped titanium dioxide (TiO2) combined with reduced graphene oxide (RGO). Cu-doped TiO2/RGO powders containing different amounts of Cu were synthesized to investigate the effect of Cu content upon the photodegradation of methylene blue in water, and were used in the preparation of sols of Cu-doped TiO2/RGO. The Cu-doped TiO2/RGO film photocatalysts showed better performance in the photodegradation of methylene blue than an undoped TiO2/RGO film. After 180 min of UV irradiation, 7.5-CTG-5 (7.5 wt% of Cu and 5 wt% of RGO) photocatalyst removed 63% of methylene blue from aqueous solution with an initial concentration of 10 ppm, whereas 0-CTG-5 (0 wt% of Cu and 5 wt% of RGO) decomposed only 28% of the methylene blue, indicating that the presence of Cu enhanced the photocatalytic activity. Doped Cu could narrow the bandgap of TiO2, thereby influencing the reduction of graphene oxide and enhancing the hydrophilicity of the materials, and thus producing the observed increase in photocatalytic activity. The relationships between hydrophilicity and photocatalytic activity are discussed herein.