The polypyrrole–zinc oxide (PPy–ZnO) hybrid sensor doped with different weight ratios of camphor sulfonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy–ZnO hybrids were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR) and UV–vis techniques which proved the formation of polypyrrole, PPy–ZnO and the interaction between polypyrrole–ZnO (PPy–ZnO) hybrid with CSA doping. The gas sensing properties of the PPy–ZnO hybrid films doped with CSA have been studied for oxidizing (NO₂) as well as reducing (H₂S, NH₃, C₂H₅OH and CH₃OH) gases at room temperature. We demonstrate that CSA (30 wt.%) doped PPy–ZnO hybrid films are highly selective to NO₂ along with high-sensitivity at low concentration (80% to 100 ppm), fast-response time (120 s) and better stability, which suggested that the CSA (30%) doped PPy–ZnO hybrid films are potential candidate for NO₂ detection at room temperature.