A simple and facile one-pot wet-chemical co-reduction method was developed for the synthesis of reduced graphene oxide supported porous PtAu alloyed nanoflowers (PtAu-nanoflowers/rGO). p-Aminopyridine was employed as a structure-directing agent and a stabilizing agent. No seed, template, surfactant, or polymer was involved in the synthesis process. It was found that the reaction temperature and the dosage of p-aminopyridine were essential for the final product. Furthermore, the as-prepared nanocomposites showed improved catalytic activity for the reduction of 4-nitrophenol in contrast to monometallic Pt nanocrystals/rGO, Au nanocrystals/rGO, and commercial Pt/C (50 wt%).