Lead sulfide (PbS) is an important binary semiconductor material due to its narrow direct band gap energy (0.41 eV, for bulk) and a large exciton Bohr radius (18 nm). In the present work, PbS thin films were deposited by using chemical bath deposition method and characterized thoroughly with the help of range of characterization techniques to study various properties. X-ray diffraction confirms the formation of cubic structure of PbS. Upon thermal heat treatment the crystallinity of the sample was found to be increased remarkably. The optical band gap 1.23 and 1.10 eV was estimated for as-prepared and heat-treated PbS thin films. Compact, void free, densely packed well adherent growth of PbS layer was confirmed by SEM images. Triangular shaped morphology was observed for as-deposited samples, whereas agglomerated cauliflower shaped clusters were formed upon annealing. Pb-rich layers were confirmed from energy dispersive X-ray analysis upon annealing due to the evaporation of elemental sulfur present at grain boundaries and on the surface of sample. Both samples revealed Schottky behavior under dark and infra-red (IR) illumination condition. The increased photocurrent measured under IR illumination demonstrated that PbS was a good candidate for IR detector. The decreased ideality factor calculated for annealed sample revealed the enhancement in the crystallinity and less leakage current through grain boundaries.