In this paper, we report on the performance of an ammonia gas (NH3) sensor based on camphor sulfonic acid doped polyaniline–zinc oxide nanocomposites fabricated by a simple spin coating technique. The nanocomposite showed the sensitivity to ammonia gas (NH3) at room temperature (300 K). Maximum response up to 28.11% was achieved for 100 ppm NH3. Depending on the concentration of NH3, the response time was ranged between 22 and 66 s, whereas the recovery time was 256–418 s.