Platinum thin films were prepared by chemical vapor deposition based on the oxidative decomposition of (methylcyclopentadienyl)trimethylplatinum [CH3C5H4Pt(CH3)(3)] as a precursor. The film growth is characterized by slow growth during the initial stage, followed by explosive growth on the initial layer. With increasing oxygen ratio and temperature, the duration of the initial stage is shortened and the growth rate on the initial growth layer is increased. However, an Arrhenius plot gives an activation energy of 0.7 eV regardless of the temperature or the oxygen ratio. Therefore, the rate-determining step of the entire reaction is the oxidative decomposition of the precursor on the growth front. On the other hand, an autocatalysis of platinum enhances the oxygen adsorption, which increases the collision frequency between the oxidizing species adsorbed and the source transferred on the growing surface. That is, the oxygen molecules that adsorbed and eventually saturated on the substrate surface shorten the duration of the initial stage and increase the growth rate, since the oxidative decomposition is enhanced by the autocatalysis of a self-seed platinum layer.