A metalorganic precursor containing Ti and Pt was synthesized using Ti alkoxide derivative, amino acid, and platinum salt. The decomposition behavior of the precursor and thin-film formation were examined in terms of microstructure evolution and crystallization. The precursor yielded anatase at 400 °C. Grain growth of platinum particles and TiO2 grains was suppressed even at 800 °C in the films. Suppression of grain growth was attributed to an effect of film thickness.