Dendritic platinum nanoparticles are straightforwardly synthesized in high yield via a one-step aqueous-phase reaction mediated by Pluronic F127 block copolymer from the reduction of a platinum complex by ascorbic acid without the need for organic solvents, templates, or ion replacements. The proposed method is unique in its simplicity. The asprepared dendritic platinum nanoparticles possess the highest surface area (56 m(2) g(-1)) of all reported unsupported platinum materials.