Many high efficiency thin-film solar cells incorporate a thin layer of CdS in the device structure to form a heterojunction. Chemical bath deposition (CBD) is the most preferred method of deposition especially for large area thin film solar cells. This study explored the effects of ammonium sulfate on the CdS film produced by CBD using cadmium sulfate as the cadmium source. The concentration of ammonium sulfate was varied from 0 M up to 0.006 M. The resulting optical, structural and surface morphological properties of the films were characterized. Results have shown that the films obtained at higher concentrations of ammonium sulfate were smoother and the occurrence of pinholes was also reduced. Agglomeration of CdS particles that is usually present in films deposited using cadmium sulfate as a precursor was also noticeably reduced. It was also observed that the rate of deposition also increased, resulting in a thicker film for identical deposition time and temperature. The average thickness of the films produced ranged from 60 nm to 180 nm.