We report a simple one-pot synthesis of PtNi-MWCNT hybrid nanostructures as a high performance and durable electrocatalyst for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). The whole approach was achieved in aqueous solution at room temperature, without using any organic solvents, templates or growth inducing catalysts. A single-crystal Pt nanoparticle was successfully grown on Ni nanoparticle surfaces using commercial Ni-coated MWCNTs as a support. PtNi-MWCNT hybrids possessed a high mass activity of 0.51 A mgPt-1, nearly double that of the state-of-the-art TKK's Pt/C catalyst. After an accelerated durability test by 2500 potential sweeping cycles, PtNi-MWCNTs still retained 89.6% of their initial mass activity, which is 0.46 A mgPt-1 and 4% higher than the DOE (Department of Energy) target of 0.44 A mgPt -1 for 2017-2020. The reported synergy between high performance and simple synthesis demonstrated that PtNi-MWCNTs could be effective cathode catalysts for high performance PEFCs. © 2014 The Royal Society of Chemistry.