Bimetallic Pt/Sn nanoparticles, synthesized by the microemulsion method, have been investigated once deposited on a boron-doped diamond (BDD) substrate electrode. Nanoparticles are in the nano-size domain and their effective composition corresponds to their expected ones. Moreover, Pt-decorated-by-Sn nanoparticles were synthesized rather than true alloys. Interestingly, these nanoparticles have exhibited superior electrocatalytic activity toward ethanol oxidation. It is believed that this surface could promote the activation of the ethanol C–C bond scission, or increase the turnover frequency of products formation. The elucidation of this point will require additional spectroscopic evidences.