A convenient method was used for synthesizing Pt-nanoparticle/MoSx/silicon nanowires nanocomposites. Obtained Pt-MoSx/silicon nanowires electrocatalysts were characterized by transmission electron microscopy (TEM). The hydrogen evolution reaction efficiency of the Pt-MoSx/silicon nanowire nanocomposite catalysts was assessed by examining polarization and electrolysis measurements under solar light irradiations. The electrochemical characterizations demonstrate that Pt-MoSx/silicon nanowire electrodes exhibited an excellent catalytic activity for hydrogen evolution reaction in an acidic electrolyte. The hydrogen production capability of Pt-MoSx/silicon nanowires is also comparable toMoSx/silicon nanowires and Pt/silicon nanowires. Electrochemical impedance spectroscopy experiments suggest that the enhanced performance of Pt-MoSx/silicon nanowires can be attributed to the fast electron transfer between Pt-MoSx/silicon nanowire electrodes and electrolyte interfaces.