In the present work, we report the room temperature NH3 sensing properties of Cobalt-boride nanoparticles intercalated polyaniline (Co-B-PANI) nanocomposite films. Polyaniline nanocomposite films (PNCF's) have been deposited at room temperatures by in-situ oxidative polymerization of aniline in the presence of Co-B nanoparticles. The PNCF exhibited a highly selective, sensitive and reversible response towards NH3. It exhibited an improved response and recovery times of 3 and 345 s, respectively towards 50 ppm of NH3. The response time in the case of PNCF was found to be better than that exhibited by pure PANI-sensor-films (7 and 400 s). Raman measurements performed before and after the exposure towards NH3 indicated a strong variation in the intensity of the peak corresponding to C=N/C-N+ stretching vibrations. Good sensitivity along with the improved response and recovery times indicated Co-B-PANI nanocomposite film to be suitable for room temperature ammonia sensing applications.