Mesoporous TiO2 thin films doped with varying amounts of cerium have been synthesized via a supramolecular-templated sol-gel route. The cerium dopant strongly affects the mesostructure, photocatalytic, and optical properties of the mesoporous TiO2 films. At an appropriately low level of cerium doping (i.e., Ce/Ti < 10 mol %), the film showed an increase in the degree of mesoscopic orderliness with an obvious degradation in the nanocrystallinity, which is related to the fact that cerium adversely affects the growth of titania nanocrystallites during thermal annealing. The photocatalytic ability of the film with Ce/Ti = 0.3 mol % was highest for degradation of methylene blue under UV irradiation, which is 3.5-fold of that of the undoped mesoporous TiO2 film. This remarkable enhancement in photoreactivity is attributed to the facilitated transferring of electrons to oxygen in association with cerium cations. The cerium-doped mesoporous TiO 2 thin films also demonstrate photoluminescence at room temperature, where the photoluminescence band exhibits a prominent decrease in intensity with the increasing level of cerium doping, which is ascribed to the cerium ions in restraining the radiative recombination of excitons by generating a considerable amount of interfacial states.