Bi2S3 thin films were prepared without complexing agent and with different concentrations of tartaric acid as a complexing agent by a spray pyrolysis technique. The effect of concentration of the complexing agent on the properties of Bi2S3 thin films was studied by characterizing the films by X-ray diffraction, scanning electron microscopy, optical absorption, and dark electrical resistivity measurement techniques. These studies revealed that all films were polycrystalline. The band gap energy for films grown without complexing agent was observed to be 1.72 eV. However, the band gap energy for different concentrations of complexing agent was observed to be 2.0 eV. The electrical resistivity of the films with complexing agent was higher than that of the film prepared without complexing agent. The electrical resistivity increased with increasing concentration of complexing agent.