Nanocomposites consisting of the bimetallic carbide Co6Mo6C2 supported on graphitic carbon (C-g) were synthesized in situ by an anion-exchange method for the first time. The Co6Mo6C2/C-g nanocomposites were not only chemically stable but also electrochemically stable. The catalyst prepared by loading Pt nanoparticles onto Co6Mo6C2/C-g was evaluated for the oxygen reduction reaction in acidic solution and showed superior activity and stability in comparison with commercial Pt/C. The higher mass activity of the Pt-Co6Mo6C2/C-g catalyst indicated that less Pt would be required for the same performance, which in turn would reduce the cost of the fuel cell electrocatalyst. The method reported here will promote broader interest in the further development of other nanostructured materials for real-world applications.