In the present work, NO2 gas sensor based on Cadmium sulfide (CdS) nanostructures were prepared by using the chemical route technique. CdS thin films of different thickness were prepared by spin coating technique with different speed (1000, 2000 and 3000 rpm). Prepared thin films were characterized by techniques, such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared spectroscopy (FT-IR) and Ultraviolet–Visible spectroscopy (UV–Vis), which offered the information about the chemical structure and morphology of CdS thin film. Gas sensing measurements for detecting 20 ppm NO2 gas were carried out on CdS thin film prepared on interdigital electrodes patterned corning glass substrate and a maximum response of ~1.73 × 102 at 70 °C operating temperature was observed. Display omitted •CdS thin film was prepared over inter digital electrodes (IDEs) by spin coating.•The hexagonal shaped surface morphology is being reported first time.•NO2 Gas sensor work at low operating temperature has been studied.•The sensing mechanism is administered by the porosity of the thin film.•The sensor has sensor response ~1.73 × 102 towards to 20 ppm.