In this study, pure ZnO and g-C3N4 were synthesized using coprecipitation and simple calcination methods, respectively. Further, ZnO is impregnated on a g-C3N4 surface with 10, 20 & 30 weight percentages, respectively. Besides, these materials are characterized by various physicochemical techniques such as PXRD, UV-Vis-DRS, TEM, PL, and FT-IR, etc. Vitally, as-prepared materials, catalytic activity was tested for removal of Rhodamine B and 4-nitrophenol from the wastewater under visible light irradiation. Among all these catalysts, 20 wt% ZnO/g-C3N4 showed better activity and showed 67% and 75% mineralization. Graphic abstract: The graphical abstract simply represents the proposed mechanism for photocatalytic removal of 4-nitrophenol and Rhodamine B with ZnO/g-C3N4 composite. ZnO was a hexagonal plate type structure and g-C3N4 shows a sheet-type structure. [Figure not available: see fulltext.] © 2021, Indian Academy of Sciences.