CO poisoning of Pt catalysts is one of the major challenges to the commercialization of proton exchange membrane fuel cells. One promising solution is to develop CO-tolerant Pt-based catalysts. A facilely synthesized Pt/FeOx catalyst exhibited outstanding CO tolerance in the oxidation of H2 and electrochemical CO stripping. Light-off temperature of H2O formation over Pt/FeOx was achieved even below 30 °C in the presence of 3000 ppm CO at a space velocity of 18 000 mL g-1cat h-1. For the electrochemical oxidation of CO, the onset and peak potentials decreased by 0.17 V and 0.10 V, respectively, in comparison with those of commercial Pt/C. More importantly, by a combination of hard X-ray photoemission spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies it was found that the decreased electron density of Pt in Pt/FeOx enhanced the mobility of adsorbed CO, suppressed Pt-CO bonding and significantly increased the CO tolerance of Pt/FeOx.