Thin films of copper nanoparticles intercalated-polyaniline nanocomposites (NC) have been deposited at room temperatures by in situ oxidative polymerization of aniline in the presence of different concentrations of Cu nanoparticles. The response characteristics of the NC thin films toward different gases namely NH 3 , CO, CO 2 , NO and CH 4 were examined at room temperature. Both pure polyaniline (PANI) and NC films exhibited a selective response toward NH 3 . Incorporation of Cu nanoparticles resulted in an improvement of the sensors response and response kinetics. The response and the recovery times of composite film toward 50ppm of NH 3 were 7 and 160s, respectively. Additionally, the NC sensor film could reversibly detect as low as 1ppm of NH 3 concentrations. The enhanced response of NC films toward NH 3 is attributed to the deprotonation and reprotonation processes as also supported by Raman investigations.