A composite nanostructure consisting of Pt nanoparticle/W nanodendrite was fabricated on an insulator Al2O3 substrate using an electron-beam-induced deposition process combined with an ion sputtering method. W nanodendrites with the tips of 3 nm were grown self-standing at the edge of the A12O3 substrate. The observed morphology is attributed to a growth mechanism involving an electrical charge-up on the substrate surface, movement of charges, and their accumulation on the convex surface of the substrate as well as at the tips of the deposits. Pt nanoparticles with an equilibrium face-centered-cubic structure were uniformly distributed on the W nanodendrites. These composite nanostructures have potential for application in the fields of catalysis and nanodevices.