PdAg bimetallic and PdAgCo trimetallic nanoparticles (NPs) are synthesized by a one-pot method in an organic solvent medium. Our results show that the catalytic activity of PdAgCo/C (1133.249 mA mg(Pd)(-1)) for formic acid oxidation (FAO) is ca. 2.4 times larger than commercial Pd/C (483.563 rnA mg(Pd)(-1)) and 1.7 times larger than PdAg/C (680.741 mA mg(Pd)(-1)). This study indicates that Co doping in PdAg bimetallic NPs can significantly improve its FAO activity. It is expected that the as-synthesized PdAgCo trimetallic NPs could be used as high-performance catalysts for direct formic acid fuel cells (DFAFCs).