Abstract <p>ZnO–CeO₂–TiO₂ (ZCT) ternary oxide nanocomposites were synthesized via a co-precipitation route and investigated in two states: as-prepared and calcined at 600°C. Phase composition and crystallinity were examined using X-ray diffraction, which confirmed the coexistence of hexagonal wurtzite ZnO, cubic fluorite CeO₂, and tetragonal anatase TiO₂ phases. The calcined sample exhibited enhanced diffraction intensity and reduced peak broadening, indicating improved crystallinity and phase development following thermal treatment. Microstructural parameters evaluated using the Debye–Scherrer and Williamson–Hall methods revealed an increase in average crystallite size accompanied by a reduction in microstrain and dislocation density after calcination. Fourier transform infrared spectroscopy confirmed the presence of characteristic metal–oxygen vibrations associated with Zn–O, Ce–O, and Ti–O bonds, along with a significant decrease in hydroxyl-related absorption bands due to dehydration and dehydroxylation processes induced by heat treatment. UV-visible diffuse reflectance spectroscopy showed strong ultraviolet absorption for both samples, with a noticeable blue shift of the absorption edge in the calcined nanocomposite, reflecting modifications in structural ordering and defect states. The study provides a systematic comparative analysis of the structural and optical characteristics of ZnO–CeO₂–TiO₂ nanocomposites before and after calcination, establishing reliable physicochemical reference data for future investigations focused on functional performance evaluation.</p>