Mesoporous Ce-doped TiO2 nanoparticles with different content of Ce are prepared by one-step hydrothermal method. The samples are characterized by XRD, TEM, Raman, XPS, BET, PL and UV–vis measurements. The results show that TiO2 doped with Ce can reduce the crystallite size. Under UV irradiation, the Ce-doped TiO2 samples exhibit much higher photocatalytic activity than pure TiO2 and commercial P25 for the degradation of Rhodamine (RhB). The maximum photocatalytic reaction rate constant for Ce-doped TiO2 sample is obtained as 0.021 min−1. The unique photocatalytic properties of Ce-doped TiO2 are attributed to the improvement of photogenerated electron–hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce3+/Ce4+. A degradation mechanism is proposed for the degradation of RhB for Ce-doped TiO2 photocatalyst under UV light.