A novel Bi2S3/ZnS heterostructure has been synthesized through an in situ cation-exchange method between ZnS and bismuth(III) chloride. The obtained samples were characterized by multiform techniques, such as X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission microscopy, UV-visible diffuse-reflectance spectroscopy, and photoluminescence spectra. The photocatalytic activities of the obtained photocatalysts were measured by the degradation of rhodamine B (RhB) and refractory oxytetracycline (OTC) under visible-light irradiation (λ ≥ 400 nm). The as-prepared Bi2S3/ZnS photocatalysts exhibit wide absorption in the visible-light region and display superior visible-light-driven photocatalytic activities in degradation of RhB and OTC compared with pristine ZnS microspheres and Bi2S3 nanorods. The dramatic enhancement in the visible light photocatalytic performance of the Bi2S3/ZnS composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. The present study provides helpful insight into the design of novel and highly efficient sulfate heterostructure photocatalysts.