Deuteration has found important applications in synthetic chemistry especially for pharmaceutical developments. However, conventional deuteration methods using transition-metal catalysts or strong bases generally involve harsh reaction conditions, expensive deuterium source, insufficient efficiency, and poor selectivity. Herein, we report an efficient visible-light-driven dehalogenative deuteration of organic halides using plasmonic Au/CdS as photocatalyst and D2O as deuterium donor. Electron transfer from Au to CdS, which has been confirmed by surface-enhanced Raman spectroscopy, plays a decisive role for the plasmon-mediated dehalogenation. The deuteration is revealed to proceed via a radical pathway in which substrates are first activated by the photoinduced electron transfer to generate aryl radicals, and the radicals are further trapped by D2O to give deuterated products. Under visible-light irradiation, excellent deuteration efficiency is achieved with high functional group tolerance and a wide range of substrates at room temperature. Compared with bare CdS, the photocatalytic activity increases ∼18 times after the loading of plasmonic Au nanoparticles. This work sheds light on the interfacial charge transfer between plasmonic metals and semiconductors as an important criterion for rational design of visible-light photocatalysts.