<p>Cs-doped SnO₂ thin films with Cs concentrations of 0, 1, 3, and 5 wt% were deposited on glass substrates by spray pyrolysis to investigate the influence of Cs incorporation on their structural, morphological, optical, photoluminescence, and electrochemical properties. X-ray diffraction confirmed the formation of single phase tetragonal SnO₂ with a preferred (110) orientation for all films. Cs incorporation promoted crystallite growth and improved the crystalline quality up to 3 wt%, while no secondary phases associated with Cs compounds were detected. Field-emission scanning electron microscopy revealed the evolution of the surface morphology from relatively fine grains for the undoped film to larger and more compact grains with increasing Cs content. Optical measurements showed that all films remained highly transparent in the visible region, with only slight variations in the optical bandgap and refractive index after Cs addition. Photoluminescence analysis indicated that Cs incorporation modified the defect-related emission, reflecting changes in the concentration of oxygen vacancy-related states. The electrochemical response toward H₂O₂ was subsequently evaluated in 0.5&#xa0;M KOH using chronoamperometry. All films exhibited a clear current response upon successive H₂O₂ additions; however, the sensing sensitivity decreased systematically with increasing Cs concentration, following the order Pure &gt; Cs-1 wt% &gt; Cs-3 wt% &gt; Cs-5 wt%. This behavior indicates that although moderate Cs incorporation improves the structural quality of SnO₂ thin films, it does not enhance their electrochemical activity toward H₂O₂ oxidation, suggesting that the sensing performance is governed primarily by the availability of electrochemically active surface sites rather than crystallinity alone. These findings provide further insight into the relationship between Cs-induced structural modifications and the functional properties of SnO₂ thin films.</p>