The electrochemical formation of oxide on metallic surfaces often changes their electrocatalytic performance. In this work, we have studied this effect on the methanol oxidation reaction by systematically controlling the PdO formation/reduction potential using Au−Pd core-shell nanocrystals with different Pd shell thicknesses. AuPd0.4 core-shell nanocrystals have a 150 mV positive shift in the PdO reduction potential with respect to Pd nanocrystals and 2.9 and 8.8 times higher charge density in the anodic and cathodic scan of cyclic voltammetry respectively. The origin of the higher activity comes predominantly from electronic effects caused by the Au core that results in higher availability of Pd sites at more positive potentials.