In this study In₂O₃ and In₂O₃:S thin films were prepared on glass substrates using the spray pyrolysis technique. The effect of sulfur impurities on the structural, morphological, electrical, thermo-electrical, optical and photoconductive properties of films has been investigated. The sulfur to indium atomic ratios (x = [S]/[In]) were varied from 0 to 15 in the spray solution. From the x-ray diffraction analysis, a phase transition occurred from the cubic In₂O₃ to the cubic β-In₂S₃ phase with increasing S-doping level. SEM images indicated that the nanostructure of the films has a particle-cluster type growth. The Hall effect measurements have shown n-type conductivity in all of the deposited films. The lowest resistance of 19 kΩ sq⁻¹ and the highest carrier concentration of 1.32 × 10¹⁹ cm⁻³ were obtained for the film deposited with an [S]/[In] atomic ratio of 0.6. The maximum of the Seebeck coefficient equal to 141 μV K⁻¹ was obtained at 400 K for the film deposited with an [S]/[In] atomic ratio of 1. The average transmittance of films varied over the range 40–80% with S-concentration. The band gap values of samples were obtained in the range of 3.85–3.96 eV. From the photoconductivity studies, the sample prepared with the [S]/[In] atomic ratio of 0.2 exhibited the highest photoconductivity among the In₂O₃:S films.