Pt-Ru nanoparticles were dispersed on Ordered Mesoporous Carbon Hollow Spheres containing Si and doped with N, to form the Pt-Ru/N-OMCHS-Si nanocatalyst. Its catalytic activity for the Ethanol Oxidation Reaction (EOR) was evaluated in acid media. Pt-Ru/N-OMCHS-Si showed a higher catalytic activity for the EOR than Pt-Ru/N-OMCHS (i.e., support without Si), monometallic Pt/N-OMCHS, Pt/C and Pt-Ru/C (where C is Vulcan XC-72). The high performance of Pt-Ru/N-OMCHS-Si was ascribed to the formation of Pt-Ru alloyed phases and the presence of Si oxides at the hollow spheres.