Graphene-ZnO nanohybrid thin films were prepared by spray pyrolysis technique at 350 °C. Different graphene nanoplate concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5 wt.% were used to deposit films on quartz substrates. The Structural and optical properties of the nanohybrid films have been investigated. X-ray diffraction XRD results show that the films have a hexagonal wurtzite polycrystalline structure and no secondary phases were observed. The structural parameters of crystallite size, dislocation density, and microstrain have indicated that the addition of graphene has a strong effect on the microstructure of zinc oxide films. Surface morphological analysis of the ZnO-graphene films reveals that the graphene content effectively modifies the morphologies and grain growth of the ZnO microstructure. It was also found from the optical properties that the maximum energy gap for pure ZnO films was 3.4 eV which decreases to 2.7 eV as the concentration of graphene increases to 0.5 wt.%. Results confirmed that graphene can be used as an efficient modifier for band gap engineering and the microstructure of ZnO thin films for enhanced photovoltaic applications.