Photostabilization of phenosafranin dye on poly(styrenesulfonate)-capped TiO2 nanoparticles has been investigated using diffuse reflectance spectroscopy. The dye degrades oxidiatively on a native TiO2 surface under visible light excitation as the excited dye participates in the charge injection process. The interaction of the dye with the semiconductor surface can be significantly reduced by capping the TiO2 particles first with poly(styrenesulfonate). The increase in fluorescence emission and decrease in dye degradation rate with increasing polymer capping suggest the protective role of poly(styrenesulfonate) capping. Diffuse reflectance laser flash photolysis studies further elucidate surface photochemical processes of phenosafranin on native and polymer-capped TiO2 nanoparticles.