Heterogeneous ZnIn2S4/g-C3N4 hybrid composites, as highly efficient visible-light-driven photocatalysts, were designed and fabricated by a simple one-step hydrothermal route for the first time, wherein the cubic ZnIn2S4 nanoparticles were in situ immobilized on the surface of porous g-C3N4 nanosheets (NSs). The resultant composites exhibit efficient photocatalytic activities, excellent photo-stability, and versatile photocatalytic abilities towards organic dye degradation, Cr(VI) reduction, and water splitting for H-2 evolution. The significant enhancement of photocatalytic activity is attributed to the effective separation of photo-generated charge carrier pairs based on the construction of close heterogeneous interface and well-matched band structure, which can obviously lengthen the life span of holes and electrons pairs. Besides, the effective charge transfer from cubic ZnIn2S4 to ultrathin g-C3N4 NSs was confirmed by photoluminescence spectra, transient photocurrent-time (I-t) curves and electrochemical impedance spectroscopy Nyquist plots. This research provides a new sight in designing the highly efficient visible light responsive photocatalysts for environmental remediation and energy production.