One-pot synthesis of carbon-supported Pd-Au alloy nanoparticles with well-defined dendritic shape (Pd-Au(den)/C) was achieved by co-reduction of K(2)PdCl(4)/HAuCl(4) mixtures in a molar ratio of 1:1 with hydrazine in the presence of Vulcan XC-72R. The prepared Pd-Au(den)/C exhibited significantly enhanced performance in the electrocatalytic oxidation of ethanol compared with dendritic Pd nanoparticles and a commercial Pd/C catalyst. PdAu(den)/C even showed higher durability in electro-oxidation of ethanol than the supported catalyst prepared by the deposition of presynthesized dendritic Pd-Au nanoparticles on the carbon support. The experimental results clearly indicate that enhanced interaction between nanoparticle catalysts and carbon support through the one-pot synthesis protocol can improve the durability of the electrocatalysts.