A series of poly(N-vinyl-2-pyrrolidone)-protected Au/Co bimetallic nanoparticles (BNPs) were prepared by a simple route based on dropwise addition of NaBH4. Their structures, particle sizes, and chemical compositions were characterized by Ultraviolet-visible spectrophotometry, X-ray photo- electron spectroscopy, Transmission electron microscopy and High-resolution transmission electron microscopy, and their catalytic activity for the hydrogen generation from hydrolysis of an alkaline NaBH4 solution was examined. As-prepared alloy-structured Au/Co BNPs had an average size between 2.8 and 3.6 nm and showed a higher catalytic activity for the hydrogen generation than the corresponding Au and Co monometallic nanoparticles (MNPs). Of all the MNPs and BNPs, Au20Co80 BNPs exhibited the highest catalytic activity, and a hydrogen generation rate of 480 mol-H2 · h(-1) · mol-M(-1) was achieved. The high catalytic activity of the BNPs can be ascribed to the formation of negatively charged Au atoms and positively charged Co atoms as a result of the electronic charge transfer effects in the BNPs.