In this study, zinc aluminate samples were synthesized using the sol–gel and the auto-combustion methods. The synthesized precursor powders were characterized by surface area analysis, particle size analysis, X-ray diffractometry technique, and scanning electron microscopy study. The X-ray diffraction pattern of both the powders, heat-treated at 1000 °C, indicated only the zinc aluminate spinel phase. The crystallite sizes were calculated from XRD data using the Debye–Scherrer equation and the results clearly showed that the auto-combustion method-derived powder had an average crystallite size of 28 nm, which was much smaller than the crystallite produced by the sol–gel route alone. The band gap energies are calculated for both samples using ultraviolent-visible diffuse reflectance spectroscopy (UV–Vis DRS), and the result showed a slight variation in band gap energy.