The activities of thin films of titania and silver-doped titania for the photocatalytic disinfection of Legionella pneumophila in aqueous medium were examined and compared with each other. Both photocatalytic films disinfected L. pneumophila under UV irradiation; the Ag-doped film showed a higher activity than the non-doped one. The silver-doped titania film even showed a slight activity in disinfecting L. pneumophila under the absence of UV irradiation. This bactericidal effect in darkness overcomes a weakness of photocatalytic disinfection. Scanning electron micrographs of L. pneumophila after photocatalytic disinfection showed that the cell walls of the bacteria were destroyed in the presence of the thin film of Ag-doped titania. Furthermore, the photocatalytic action caused decomposition of the endotoxin leaked from the dead bacteria.