Surface-enhanced IR absorption spectroscopy (SEIRAS) is so sensitive as to detect surface species at submonolayer coverages and available even in the presence of gas- or liquid-phase medium that absorb IR intensively. In the present study, we report in situ SEIRAS observation of the photoenhanced adsorption of water on thin TiO2 films coated with an island Au film. The O-H stretching of photoadsorbed water appeared at lower frequencies than that of physisorbed water, indicating stronger interactions among the photoadsorbed species. The addition of oxygen suppresses significantly the photoadsorption of water and reduces the amount of photoadsorbed water in the dark.