Heterogeneous catalysis is widely known as an efficient, clean, and low-cost technology to mitigate the environmental pollution of industrial effluents. This research aimed at optimizing the preparation and characterization of efficient g-CN/CoO nanocomposite for catalytic removal of Rhodamine B (Rh B) dye. The detected XRD peaks for the prepared nano-CoO are matched with the cubic crystal structure. In contrast, the broad peak at 27.3° corresponding to the graphite reflection of hkl (002) was noticeably weakened in the XRD pattern of the g-CN/CoO composite. FTIR spectra of g-CN/CoO nanocomposites revealed the active vibrational modes of each CoO and g-CN component. The microstructure study of g-CN showed the strong interlayer stacking of carbon nitride nanosheets, while the surface morphology of g-CN/CoO nanocomposite revealed a hybrid particulate system. EDS analysis indicated that the spot area of g-CN/CoO confirmed the chemical ratios of carbon, nitrogen, cobalt, and oxygen. BET measurements of g-CN/CoO showed a significant increase in the surface area and pore volume of single components due to the lamination of stacked g-CN nanosheets by the intercalated CoO nanoparticles. The prepared 30% g-CN/CoO revealed the lowest value of E ~1.2 eV and the highest light absorptivity suggesting strong promotion for the photocatalytic performance under visible light. The maximum photocatalytic activity of about 87% was achieved by 30% g-CN/CoO due to the photonic enhancement, which reduces the recombination of excited electrons. The developed nanocomposite with a g-CN/CoO ratio of 0.3 exhibited high stability in its photocatalytic performance after four recycling times, and a slight decrease of about 7% was estimated after the 5th reuse test.