Indium sulfide (In2S3) films with three different thicknesses (150, 400 and 600 nm) were prepared using thermal evaporation at room temperature. As prepared samples were amorphous and subsequent annealing at higher temperature (> 573 K) resulted in the formation of crystalline phase. Optical band gap was found in the range of 1.9-2.9 eV for as prepared samples and decreased with increase in annealing temperature. Interference fringe like structure in transmission spectra revealed that the films were fairly smooth and reflective. Variations in electrical resistivity and photosensitivity as a function of film thickness and annealing temperature were studied. X-ray Photoelectron Spectroscopic (XPS) studies clearly indicated uniform distribution of both indium and sulphur along the film. Energy Dispersive X-ray analysis showed that as prepared samples were stoichiometric.