Titanium dioxide nanoparticles were prepared via a photoassisted sol-gel method in which ultraviolet light irradiation was used in the preparation process of TiO2 colloid. After characterization by X-ray diffraction, X-ray absorption near-edge structure MANES) at the Ti K-edge, laser Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, it was found that the amorphous titania nanoparticles prepared by a photoassisted sol-gel method can be transformed into crystalline anatase phase at lower calcination temperature compared to those prepared by a conventional sol-gel method. In addition, the particle size distribution of anatase powder samples is also affected by UV illumination on the colloid. It is suggested that UV illumination can induce the formation of oxygen vacancies on the colloid and this results in the accelerated phase transition from amorphous to anatase titania.