This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation and charge transfer to TiO2 on FeOx–TiO2 cosputtered film. The transients which were photo-induced by femtosecond laser pulses at 545 nm (25 fs) were identified, in addition to the concomitant bleaching bands at <440 nm. Electron trapping at 150 fs was observed to compete with electron–hole recombination. A regularized inverse Laplace transform of the transient decay kinetics was worked out to determine the lifetime of the transients. About 50% of the charge carriers recombined within 500 fs, less than 50% of the charges recombined within 25 ps and a small percentage remained trapped. The transient decay within 500 ps did not decay to zero. This is the evidence for the photo-induced charges in FeOx–TiO2 leading subsequently to bacterial inactivation in the minute range. The second part of this study addresses the details of the FeOx–TiO2–PE photocatalyst performance during E. coli inactivation under solar light irradiation. The bacterial inactivation kinetics was similar under solar or visible light irradiation (>400 nm). This observation unexpectedly confirms the role of FeOx absorbing light in the visible region. The important role of TiO2 is reported, leading to bacterial inactivation in the FeOx–TiO2 co-sputtered films.