A reduced graphene oxide–Fe₃O₄–NiO hybrid nanocomposite was synthesized using a surfactant free in situ hydrothermal method. The resulting hybrid nanocomposite contained a uniform distribution of nickel oxide nanoparticles and cubic structured Fe₃O₄. The photocatalytic degradation of color and COD elimination was examined experimentally using a visible light irradiation source. The synthesized hybrid nanocomposite was characterized using a range of techniques such as XRD, FE-SEM with EDX and EPMA, HR-TEM with SAED pattern, XPS spectra and Raman spectra analysis. The mechanism and kinetics of dye degradation by the rGO–Fe₃O₄–NiO hybrid nanocomposite were examined. The results confirmed that the 2 wt% G–Fe₃O₄–NiO hybrid nanocomposite degraded 99% of both methyl red and crystal violet dyes rapidly within 15 min; 97% of effluent dye was degraded within 60 min and 87% of the influent dye was degraded within 300 min under visible light sources. Therefore, the synthesized hybrid nanocomposite is an effective catalyst with potential applications in industrial wastewater treatment to remove hazardous pollutants.