Gold (Au) nanoparticles having a Pt-shell layer (Au-Pt) deposited on a conductive support are a promising electro-catalyst for fuel cells, enabling the minimal use of Pt. We describe a facile one-pot method to grow Au-Pt having a 3.8-nm diameter on multiwalled carbon nanotubes (MWNTs) in the absence of a reducing agent, in which polybenzimidazole was used as the binding sites on the MWNTs to load the Au-Pt.