g-C3N4/ZnO Fenton-like catalysts were prepared by impregnation of g-C3N4 with a solution of zinc nitrate hexahydrate followed by calcination. XRD, FT-IR, XPS, HRTEM, SEM, and other characterization techniques were used to assess the chemical composition, morphology, and structure. The Fenton-like catalytic activity of g-C3N4/ZnO composites was measured in the removal of organic pollutants. The results showed that the g-C3N4/ZnO Fenton-like catalyst can efficiently remove the organic pollutants than pure g-C3N4. The removal efficiency of organic pollutants by g-C3N4/ZnO composite was of 89%, which is 4 times higher than that of pure g-C3N4. This clearly shows a significant improvement in the Fenton-like catalytic activity of g-C3N4/ZnO. This improved result was explained by the production of hydroxyl radicals in the g-C3N4/ZnO-H2O2 catalytic system, in a similar way as in the mechanism involved in the Fenton-like degradation. The formation of coordinate covalent bonds between N and Zn in g-C3N4/ZnO catalyst played an important role in the removal of organic dye, and thus considered another key factor of the excellent activity.