Indium tin oxide (ITO) synthesized by a glycine nitrate process has been explored as a support for Pt nanoparticles using preformed Pt colloidal particles. X-ray diffraction and energy-dispersive spectroscopic analysis in scanning electron microscopy indicate that Sn is well incorporated into the In2O3 lattice and ITO has a crystallite size of 26 nm. High resolution transmission electron microscopy shows that the Pt nanoparticles with a crystallite size of similar to 4 nm are highly dispersed on the surface of ITO nanoparticles. The ITO-supported Pt nanoparticles exhibit a higher intrinsic activity for methanol electro-oxidation with high stability during potential cycling than carbon-supported Pt despite the larger particle size of ITO and the lower electrochemical active area. Stripping experiments with CO reveal that the oxidation of adsorbed CO begins at a lower potential with ITO-supported Pt compared to that with carbon-supported Pt, indicating that the high catalytic activity is related to the active participation of ITO in the methanol oxidation process. The results suggest that ITO could be considered as an alternative support for electrocatalysts in fuel cells.