Bimetallic nanoparticles (NPs) have emerged as an important class of catalysts. In many cases, bimetallic alloy NPs have higher catalytic efficiencies than their monometallic counterparts, owing to strong synergy between the metals. In this Review, we survey the research progress on the synergistic effect of bimetallic alloy NPs for catalytic reactions related to fuel cells, such as the electrochemical oxidation of MeOH, EtOH, and formic acid, CO oxidation, the oxygen-reduction reaction, and the dehydrogenation of ammonia borane, formic acid, hydrous hydrazine, hydrazine borane, etc. In addition, the use of synergistic catalysis in some other important reactions has also been reviewed. Recent developments in synergistic catalysis over bimetallic alloy NPs will provide access to a variety of low-cost and high-performance catalysts for laboratory and industrial applications within the next few years.