Polyaniline thin films doped with an inorganic acid were deposited on glass substrate using simple and cost effective oxidative polymerization technique. Assynthesized  thin film of polyaniline was studied with different characterization techniques. The formation of polyaniline on glass substrate was confirmed by X-ray diffraction and UV spectroscopy. Surface morphological investigation was performed using scanning electron microscopy. Gas sensing behavior of polyaniline thin film was studied by I–V measurements before and after liquefied petroleum gas (LPG) exposure at room temperature, based on change in electrical resistance. The observed result shows polyaniline thin film sensor is efficient for LPG detection at room temperature.