The synthesis of nickel decorated platinum core-shell nanocatalyst for the oxygen reduction reaction (ORR) in acid media is presented. The nanocatalysts prepared through colloidal reduction of NiCl2 with NaBH4 produce Ni core and subsequent reduction of H2PtCl6 enables the core-shell structure. Heat-treatment of as-prepared Ni@Pt in hydrogen atmosphere causes change in surface structure due to strong segregation of remaining Ni particle on topmost layer of Ni@Pt alloy, while performing different cycle in cyclic voltammetry remove the top layer of Ni particle; additionally a markedly Ni@Pt stabilization favor the enhanced electrocatalytic activity toward ORR. Ni@Pt core-shell structure was physical characterized using XRD, SEM and TEM techniques. Results indicate average particles of about 7.5 nm in size. Cyclic voltammetry on thin-film rotating disk electrode reveals that Ni@Pt nanoparticles, before and after thermal treatment, have more than twice enhanced catalytic activity than Pt nanoparticles synthesized by the same way. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.