Er3+–Yb3+-codoped titania–zirconia composites were synthesized using a coprecipitation method with aqueous ammonia as the precipitator. Their crystal structures and upconversion luminescent properties were investigated using X-ray diffraction and photoluminescence spectra. The strong green and red upconversion emissions were observed. The ratio of green to red emission was changed with the variation of the host composition and dopant concentrations. The relevant mechanism was discussed.