Platinum-based alloys have been extensively shown to be effective catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Most of these catalysts are nanoparticles without shape control. Recently, extended Pt(3)Ni(111) surfaces prepared in ultrahigh vacuum were demonstrated to possess enhanced ORR catalytic activity as compared to the state-of-the-art carbon supported Pt (Pt/C) nanoparticle catalysts. How and whether this promising surface can be transformed into practical nanoscale electrocatalysts used in PEMFCs remain a challenge. We report a new wet-chemical approach of preparing monodisperse Pt(3)Ni nanoctahedra and nanocubes terminated with {111} and {100} facets, respectively. We further show that the ORR activity on the Pt(3)Ni nanoctahedra is approximately 5-fold higher than that of nanocubes with a similar size. Comparison of ORR activity between carbon-supported Pt(3)Ni nanoctahedra and commercial Pt/C reveals that the Pt(3)Ni nanoctahedra are highly active electrocatalysts. This synthetic strategy may be extended to the preparation of other shape-controlled fuel cell electrocatalysts.