In this study, the effect of reaction pH on the formation of zinc sulfide/graphene oxide (ZnS/GO) nanocomposites was investigated using a one-step hydrothermal synthesis method. Zinc acetate and sodium sulfide were employed as precursor materials, while graphene oxide (GO) was used as a substrate for the growth of ZnS nanoparticles. The influence of the reaction pH on the formation and structural characteristics of the resulting material was systematically evaluated. The results demonstrated that the formation of the composite was strongly dependent on the reaction pH. An acidic medium favored the formation of the target material, whereas no distinct formation of the nanocomposite was observed under neutral and alkaline conditions. X-ray diffraction (XRD) analysis confirmed the formation of crystalline ZnS through the appearance of its characteristic diffraction peaks. Raman and Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of GO and its oxygen-containing functional groups. In addition, energy-dispersive X-ray spectroscopy (EDX) verified the presence of carbon, oxygen, zinc, and sulfur, which was consistent with the successful formation of the prepared composite. These findings indicate that pH is a critical parameter in controlling the formation of the material during the hydrothermal process. The one-step hydrothermal method provides a simple and controllable approach for the preparation of ZnS/GO nanocomposites with potential applications in photocatalytic and environmental remediation processes.