N-doped carbon encapsulated Co3O4 nanoparticles (Co3O4@C-N) is synthesized as synergistic catalyst for oxygen reduction reaction (ORR) in acidic media. Due to inter-molecular force, scanning electronic microscope (SEM) show that the Co3O4@C-N particles with different sizes form a cocoon-like aggregated structure. The half-wave potential of the linear sweep voltammograms of Co3O4@C-N in O-2-saturated 0.1 M HClO4 solution is slightly lower than that of commercial Pt/XC-72 (20 wt.%), but its limited diffusion current density is similar to that of Pt/XC-72 in acidic media. Although the ORR activity of Co3O4@C-N is still a little lower than that of commercial Pt/XC-72, its low cost, long term-operating durability and excellent CH3OH tolerance render it as a potential alternative to Pt-based catalysts for ORR. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.