In-doped tin (II) sulfide nanoparticles (NPs), synthesized by ultrasonication method and their optical and photovoltaic properties, have been investigated. FESEM images show NPs which have a flower-like morphology that sizes are <100 nm. Optical energy band gap estimation of tin sulfide NPs with the Tauc plot method had shown an increase with minimum of indium concentration and then decreases with higher concentration of indium. Photovoltaic experiment shows the highly photovoltaic efficiency of tin sulfide NPs with indium doping, can be obtained.