Platinum nanoparticles supported on mesoporous carbon were obtained by an impregnation and reduction method with NaBH₄ as the reducing agent. The high specific surface area mesoporous carbon was obtained by carbonization of a resorcinol-formaldehyde polymer with a cationic polyelectrolyte as a soft template. Surface characterization performed by transmission electron microscopy and powder X-ray diffraction showed a homogeneous distribution and high dispersion of the metal particles on the mesoporous support. The carbon-supported Pt catalyst was employed as cathode catalyst in a direct methanol fuel cell where a 30% increase in power density was obtained when compared to Pt supported on Vulcan carbon, under the same conditions.