We report on the influence of a series of transition-metal-substituted Wells-Dawson (P2W17 (MO62(12 - n)-)-O-n; M = W-VI, Fe-II, Co-II, Ru-II) and Keggin (PW12O403- and PCoW11O395-) anions on the oxygen reduction reaction (ORR) at Au, Pd, and Pt. Wells-Dawson POMs adsorbed on Au lead to large positive shifts of the ORR potential. The magnitude of the shift depends on the transition metal and is explained using a simple thermodynamic model. The best cathode performance was achieved using a PCoW11O395- Cocatalyst and a Pt cathode. The +54 mV positive shift in the ORR potential that we observed is comparable to the performance of the best-known bimetallic catalysts.