Carbon-supported Pt/MoOx anode catalysts were prepared by the preimpregnation, postimpregnation, and chemical reduction methods. The physicochemical characteristics of all catalysts were determined by X-ray diffraction, scanning transmission electron microscopy, and CO pulse titration. The electrochemical oxidation of CO verified from CO-stripping voltammetry shows that most of the COads were oxidized on the Pt sites. The Pt/MoOx/C catalyst prepared by the chemical reduction method showed superior hydrogen electrochemical oxidation in pure H-2, apparently due to the much smaller Pt particle size than those of the other Pt/MoOx/C catalysts. However, the anode performances in the presence of 500 ppm CO/H-2 mixture showed that a catalyst with high CO tolerance was derived from the Pt/MoOx/C catalyst prepared by postimpregnation method. The oxidation of CO by the water-gas shift (WGS) reaction is shown by the formation of CO2 even under an open-circuit condition. With an increase in current, active sites for the WGS reaction is regenerated by electrochemical oxidation of hydrogen. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3223970] All rights reserved.