In this work, we report for the first time the improvement of the photovoltaic characteristics of DSSCs by mixing TiO2 with WO3. WO3 reduced the surface trap states of TiO2, which suppressed the charge recombination and increased the driving force of electron injection, thereby improving its power conversion efficiency. It was observed that DSSCs fabricated using the WO3-mixed TiO2 films show the maximum conversion efficiency of 4.84% because of the effective prevention of the electron recombination. DSSCs based on WO3-mixed TiO2 films showed better photovoltaic performance than cells fabricated with only TiO2 nanoparticles.