Single-walled carbon nanotubes (SWNTs) have been used as electrocatalyst support for fuel cells. A toluene solution of a platinum salt, bis(dibenzylideneacetone) platinum, has been used for the first time to decorate the outer surface of SWNT bundles with Pt nanoparticles. The obtained Pt/SWNT materials were then used as catalytic layer in electrodes for fuel cell electrocatalysis. The used platinum salt concentration in the initial SWNT dispersion determined the Pt nanoparticle size and, consequently, the activity of the Pt/SWNT electrodes toward the oxygen reduction reaction. The achieved results were compared with those corresponding to a commercial Pt/carbon black catalyst with similar Pt loading and surface area.