We report the synthesis of graphene-TiO2 (G-TiO2) composite films that exhibit significantly enhanced photoelectrochemical water-splitting performance relative to pure TiO2. Supersonic kinetic spraying was used to produce strongly adhered, electrically and mechanically robust G-TiO2 composite films containing 0.1, 0.5, 1.0, and 5.0 wt.% graphene. Films with an intermediate graphene content of 1.0 wt.% demonstrated the best water-splitting performance. G-TiO2 composite films with 1.0 wt.% graphene exhibited photocurrent density ten times that of pure TiO2 films. The electron transfer between TiO2 and graphene suppresses the recombination of photoinduced charge carriers and prolongs the electron excited-state lifetime, which contributes to the enhanced photoelectrochemical water-splitting performance.