Titanium oxide has been widely used as an external additive for electrophotographic toners. One of the factors that titanium oxide contributes to toner performance is the improvement of charge stability. In this study, we investigated the triboelectric charging behaviors of titanium oxide doped polyester films in contact with iron carrier beads. As a result, it was found that the humidity dependence of triboelectric charging was reduced for films containing anatase type titanium oxide, but was not for films doped with rutile type titanium oxide.