This article reports a novel ternary nanocomposite consisting of ZnO, g-C₃N₄, and graphene oxide (GO) that provides enhanced photocatalytic performance and stability. The ZnO nanospheres disperse evenly and embed themselves in the porous g-C₃N₄. Composites with various g-C₃N₄ and GO to ZnO weight ratios were synthesized and characterized systematically. The results indicated that the absorption of binary g-C₃N₄/ZnO nanocomposites shifted to a lower energy compared to pure ZnO in a fashion consistent with the loading content of g-C₃N₄. Notably, the loading content of GO in the ZnO–g-C₃N₄ composite resulted in increased absorption in the visible range and improved charge separation efficiency, thereby drastically improving photocatalytic activity. Successful hybridization of ternary nanocomposite was confirmed by drastic quenching of fluorescence and broader visible light absorption. The optimal content of g-C₃N₄ in the ZnO–g-C₃N₄ composite was 50%, which exhibited the effective hybridization between ZnO and g-C₃N₄, and high photocatalytic efficiency. However, the photocatalytic degradation of the ternary nanocomposite showed performance that was two times greater than ZnO–g-C₃N₄, exhibiting 99.5% degradation efficiency after just 15 min of light irradiation. The combined heterojunction and synergistic effects of this composite account for the improved photocatalytic activity.