The effect of the modification of Pd-based electrocatalysts by molybdenum on the catalytic performance toward ethanol oxidation in the alkaline solution is investigated. The results indicate that the molybdenum oxide/hydroxide assists in the uniform distribution of Pd nanoparticles on the surface of the carbon support. The catalytic performance of the Mo-modified Pd/MWCNT catalyst is largely dependent on the temperature at which the molybdenum oxide/hydroxide is heat-treated. The catalyst prepared from the molybdenum oxide/hydroxide heat-treated at 350 A degrees C has the highest catalytic activity and the best poison resistance. X-ray photoelectron spectroscopy results reveal that there is an interaction between Pd and Mo in Mo-modified Pd/MWCNT catalysts. The moderately dehydrated and oxidized molybdenum oxide/hydroxide has the strongest effect on promoting the catalytic activity and the poison resistance of Pd-based nanocatalysts for ethanol oxidation.