A facile and efficient visible-light-mediated method for directly converting sulfides into sulfoxides under clean conditions without using any photocatalysts is reported. This method exhibited favourable compatibility with functional groups and afforded a series of sulfoxides with high selectivity and yields. Moreover, in order to shed more light on such a transformation, detailed mechanism studies were carried out both experimentally and theoretically. The readily accessible, low-cost and eco-friendly nature of the developed method will endow it with attractive applications in chemical synthesis.