In this study, TiO2 nanoparticles (NPs) /reduced graphene oxide (RGO) composites were prepared by hydro thermal process and physiochemical, optical, photocatalytic and photoelectrochemical properties of prepared materials was investigated. Photocatalytic activity measurement showed that methylene blue (MB) photo degraded faster by TiO2-RGO composites compared to bare TiO2. Furthermore, photoelectrochemical (PEC) properties of TiO2 and TiO2-RGO electrodes were investigated under the illumination of a 150 W Xe lamp in 1M aqueous solution of KOH as the electrolyte. Moreover, TiO2-RGO electrodes showed greatly improved photo current density which is 3.3-fold higher than pure TiO2. Combined analyses of Mott-Schottky plots and electrochemical impedance spectroscopy (EIS) confirmed that RGO in the TiO2-RGO nanocomposite increased the donor concentration (N-D), decreased recombination process of charge carriers (tau(D)), thinner the space charge layer (W-SCL) and reduced fiat band potential (V-Fb) of the TiO2, thereby greatly enhancing the PEC performances of the TiO2 photoanodes. The improved PEC performance of the TiO2-RGO nanocomposite compared to TiO2 NPs attributed to great enhancement of electron transport through the RGO in the TiO2- RGO film and consequently charge separation.