Abstract: The ZnO/g-C3N4 composite was synthesized through facile one step calcination method using urea and zinc acetate dehydrate precursors. A series of techniques, TGA (Thermogravimetric Anal.), XRD (X-ray Diffraction), FTIR (Fourier Transform IR), BET (Brunauer-Emmett-Teller) surface area, SEM (SEM), TEM (Transmission Electron Microscopy), XPS (XPS), UV-Visible DRS (Diffuse Reflection Spectroscopy), PL (Photoluminescence) and EIS (Electrochem. Impedance Spectroscopy) were used to evaluate the physicochem. and optical properties of composites. In the presence of sacrificial electron donor EDTA, ZnO/g-C3N4 photocatalyst gave better visible light response photocatalytic reduction ability against Cr(VI). The enhanced photocatalytic performance of ZnO/g-C3N4 photocatalyst could be ascribed to the addition of ZnO. The heterojunction effects between ZnO and g-C3N4 result in better photogenerated charge separation and slower e- - h+ pairs recombination, which was confirmed from PL, EIS and UV-Visible DRS. The influence of various factors such as ZnO amount in the composite, synthesis calcination condition, catalytic dosage, initial concentration of Cr(VI), EDTA concentration and solution pH have been optimized for the photocatalytic Cr(VI) reduction Moreover, ZnO/g-C3N4 composite showed modest stability after five cycle. Furthermore, the reaction mechanisms and pathways for Cr(VI) reduction by ZnO/g-C3N4 were proposed. HighlightsPhotocatalyst ZnO/g-C3N4 composite was prepared by facile single-step calcination method for Cr(VI) reduction Prepared composite showed excellent photocatalytic Cr(VI) reduction efficiency. Effective charge transfer ability of the composite was observed Photogenerated e- - h+ pairs recombination process was decreased. EDTA enhanced the photocatalytic Cr(VI) reduction as hole scavenger. Graphical abstract: [graphic not available: see fulltext]