Controlling the synthesis of noble metal nanostructures with highly branched morphology to obtain specific physical and chemical properties has attracted much attention. This paper reports the synthesis of 3D Pt nanodendrites with controlled architectures (multibranched) by a simple one-pot hydrothermal reaction in the presence of fructose. At high reaction temperature, fructose not only acts as a reducing agent, but also forms a hydrothermal carbon, which, as a capping agent, is absorbed on the surface of metal nanocrystals and induces the anisotropic growth of Pt nanodendrites. The prepared Pt nanodendrites are highly porous, and have self-supported nanoarchitectures with a high surface area and a number of absorption sites for reactant molecules. The Pt nanodendrites exhibit a higher electrocatalytic activity and stability than commercial Pt/C for methanol oxidation reaction.