SnS/CdS heterojunction is a promising system for photovoltaic application. SnS thin films were thermally evaporated onto CdS/ITO coated glass substrates. The structure of the device was glass/ ITO/CdS/SnS/In/Ag and I-V curves of the fabricated devices were measured under dark and illuminated conditions, respectively. We discussed the relationship of the thickness and annealing temperature of CdS buffer layers with the performance of SnS/CdS heterojunctions. The optimum thickness and annealing temperature of the CdS buffer layers were 50 nm and 350°C, respectively. The best device had a conversion efficiency of 0.0025%.