The co-precipitation method was used to synthesize ZnO nanoparticles (NPs). Then, graphene oxide (GO) sheets which were reduced during the reaction process to become (rGO), were embellished with ZnO NPs. The impact of rGO on the structure and morphology of ZnO was investigated using XRD, FTIR, TEM, and SEM techniques. Investigating the optical characteristics was done using UV–vis spectroscopy. ZnO exhibits a hexagonal phase, as proved by XRD. The average crystallite size reduced from 22 to 18 nm after being anchored on rGO sheets. TEM and SEM testify to the presence of ZnO in nanoscales with quasi-spherical shapes, which dispersed homogeneously along the GO sheets. The optical bandgap was increased from 2.57 eV to 3.17 eV for ZnO and ZnO-rGO, respectively. Based on the obtained optical bandgap, the refractive index of ZnO and ZnO-rGO nanocomposite was theoretically determined using different models such as Moss and Ravindra models. ZnO-rGO nanocomposite's ability to change optical characteristics makes it a superior nominee for optoelectronic applications.