This study investigates the optical and structural properties of thermally evaporated cadmium telluride (CdTe) thin films with emphasis on quantum confinement effects associated with nanoscale grains (quantum-dot-like features). CdTe is a II–VI semiconductor with a direct band gap near 1.45 eV and high absorption coefficient in the visible range, making it attractive for photovoltaic and infrared optoelectronic applications. CdTe films were deposited by thermal evaporation onto three substrate types: glass (sample No. 04), photoglass (sample No. 06), and sitall (sample No. 07). Optical spectra were measured in the 200–1200 nm range, revealing strong ultraviolet absorption attributed to high-energy interband transitions. A systematic blue shift of the absorption edge was observed for the sitall-based film, indicating an increase in the optical band gap that is consistent with quantum size effects. Band-gap energies were extracted from Tauc plots for direct transitions, yielding ~1.45 eV for the glass substrate (close to bulk CdTe) and higher values (~1.48–1.52 eV) for photoglass and sitall films. Structural characterization by SEM/EDS and AFM indicates nanoscale grains and a tellurium-rich composition, which is favorable for p-type conductivity. The dielectric response was interpreted using a Drude–Lorentz model, where the Drude term accounts for free-carrier effects that enhance infrared reflectance for photoglass and sitall substrates. The results demonstrate that substrate selection and deposition conditions can tune both the optical band gap and free-carrier response of CdTe films, enabling optimization for solar-cell absorber layers and infrared photodetector applications. Future work will focus on controlled doping and process optimization to improve uniformity and device-relevant performance.