Au/Pd bimetallic nanoparticles (BNPs) were prepared by simultaneous reduction method using NaBH4 as a reducing reagent. The effects of particle size, electronic structure and composition upon the catalytic activities of the BNPs for aerobic glucose oxidation were investigated. The PVP-protected Au/Pd BNPs of about 2.0 nm in diameter synthesized via rapid injection of NaBH4 possessed a high catalytic activity for aerobic glucose oxidation. The catalytic activity of BNPs with the Au/Pd atomic ratio of 60/40 was more than two times higher than that of Au nanoparticles (NPs) though the latter were smaller. This can be ascribed to the presence of negatively charged Au atoms arisen from electron donation from neighboring Pd atoms via electronic charge transfer. In contrast, Au/Pd BNPs synthesized via dropwise addition of NaBH4 into the starting solution and having the large mean particle sizes, showed a low catalytic activity.