We demonstrate for the first time that Bi and BiAg alloy nanospheres, fabricated with a facile hydrothermal method, display evident photocatalytic H₂ production activities. Element Bi can serve as an active photocatalyst for both water splitting and photoelectrochemical applications. More interestingly, these activities of Bi can be greatly enhanced by introducing Ag to form BiAg alloy nanoparticles, which may be ascribed to the improved charge separation and enlarged carrier concentration. The constituent of the BiAg alloy can be rationally tuned by varying the amount of Ag nanowires, and it is found that Bi_0.7Ag_0.3 exhibits the highest photoelectrochemical property.