Photoinduced SO₂ fixation on anatase TiO₂ films was studied by in situ Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The TiO₂ films were prepared by reactive DC magnetron sputtering and were subsequently exposed to 50 ppm SO₂ gas mixed in synthetic air and irradiated with UV light at substrate temperatures between 298 and 673 K. Simultaneous UV irradiation and SO₂ exposure between 373 and 523 K resulted in significant sulfur (S) deposits on crystalline TiO₂ films as determined by XPS, whereas amorphous films contained negligible amounts of S. At substrate temperatures above 523 K, the S deposits readily desorbed from TiO₂. The oxidation state of sulfur successively changed from S⁴⁺ for SO₂ adsorbed on crystalline TiO₂ films at room temperature without irradiation to S⁶⁺ for films exposed to SO₂ at elevated temperatures with simultaneous irradiation. In situ FTIR was used to monitor the temporal evolution of the photoinduced surface reaction products formed on the TiO₂ surfaces. It is shown that band gap excitation of TiO₂ results in photoinduced oxidation of SO₂, which at elevated temperatures become coordinated to the TiO₂ lattice through interactions with O vacancies and form sulfite and sulfate surface species. These species makes the surface acidic, which is manifested in nondetectable adherence of stearic acid to the modified surface. The modified films show good chemical stability as evidenced by sonication and repeated recycling of the films. The results suggest a new method to functionalize wide band gap oxide surfaces by means of photoinduced reactions in reactive gases at elevated substrate temperatures. In the case of anatase TiO₂ in reactive SO₂ gas, we here show that such functionalization yields surfaces with excellent oleophobic properties, as probed by adhesion of stearic acid.