TiO 2 thin films were deposited on unheated and heated glass substrates at an elevated sputtering pressure of 3 Pa by radio frequency (RF) reactive magnetron sputtering. TiO 2 films deposited at room temperature were annealed in air for 1 h at various temperatures ranging from 300 to 600 Β°C. The structural and optical properties of the thin films were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and ultraviolet-visible-near infrared (UV-VIS-NIR) spectrophotometry. XRD results show that as-grown and post-annealed TiO 2 films have anatase crystal structure. Higher substrate and annealing temperatures result in a slight increase of crystallinity. TiO 2 films deposited at different substrate temperatures exhibit high visible transmittance and the transmittance decreases slightly with an increase in annealing temperature. The refractive indices (at k = 550 nm) of the as-deposited and annealed films are found to be in the range of 2.31-2.37 and 2.31-2.35, respectively. Extinction coefficient decreases slightly with increasing substrate and annealing temperatures. The indirect and direct optical band gap of the as-grown films increases from 3.39 to 3.42 eV and 3.68 to 3.70 eV, respectively, with the increase of substrate temperatures. Annealed TiO 2 films also exhibit an increase in the values of indirect and direct optical band gap.