A series of Y-doped TiO2 branched nanorod arrays with different Y content were synthesized by hydrothermal approach. Incorporation of Y3+ into the rutile TiO2 lattice was confirmed by x-ray photoelectron spectroscopy measurement. The effect of Y dopant on the morphology, structure, optical properties and photoelectrochemical performance of TiO2 branched nanorod array thin films was investigated by x-ray diffraction, field-emission scanning electron microscopy, UV–vis spectroscopy, photoluminescence spectroscopy and electrochemical workstation. The length of TiO2 branched nanorod arrays varied with the amount of Y dopant. Y-doped TiO2 exhibited the enhanced visible-light absorption ability and the reduced optical band gap energy compared with the pure TiO2. It was found that TiO2 branched nanorod array thin film electrode with Y/Ti molar ratio of 3% possessed the optimal electron transport behavior, which can be ascribed to the enhancement of visible-light utilization efficiency, the narrowest band gap energy, the lowest charge recombination rate and the highest photo-excited electron yield.