<p>Transparent conducting oxide (TCO) thin films are essential components of flexible optoelectronic devices, including wearable sensors, transparent displays, photovoltaic systems, and smart electronic platforms. In this study, transparent conducting SnO₂ thin films were fabricated on flexible polyethylene terephthalate (PET) substrates using a low-cost spray pyrolysis technique followed by controlled annealing treatment. The novelty of the work lies in the systematic optimization of deposition conditions to establish correlations among microstructural evolution, optical transparency, electrical conductivity, and mechanical flexibility. X-ray diffraction analysis confirmed the formation of polycrystalline tetragonal rutile SnO₂ with a dominant (110) preferred orientation. Increasing substrate temperature enhanced crystallinity and grain growth, resulting in crystallite sizes ranging from 14.8 to 33.1 nm. The optimized film deposited at 350&#xa0;°C exhibited a high visible transmittance of 89.6%, optical band gap of 3.95 eV, sheet resistance of 18.4 Ω/sq, and electrical conductivity of 642 S/cm. Morphological investigations revealed uniform nanocrystalline grains, reduced surface roughness, and improved grain connectivity, which contributed to enhanced charge transport and optical transmission. Mechanical flexibility testing demonstrated excellent durability, with the optimized film retaining more than 94% of its initial conductivity after 1000 bending cycles at a curvature radius of 10 mm. Comparative analysis with previously reported flexible SnO₂ electrodes indicates competitive optoelectronic performance achieved through a scalable and cost-effective fabrication route. The findings provide valuable insight into the structure–property relationships governing flexible transparent conducting SnO₂ films and support their potential application in next-generation flexible optoelectronic devices.</p>