The PANi-SnO₂ hybrid nanocomposite based thin films doped with 10-50 wt % CSA were deposited on the glass substrates using the spin coating technique. The sensor response in relation to the CSA doping concentration and the gas concentration has been systematically studied. A significant sensitivity (91%) towards 100 ppm NH₃ operating at room temperature is observed for the 30 wt % CSA doped PANi-SnO2 nanohybrid. The sensing mechanism of CSA doped PANi-SnO₂ materials to NH₃ was presumed to be the effect of p–n heterojunctions.