•Pure and W-doped ZnO films were synthesized using sputtering at 0.4Pa and 1.33Pa.•The doped film deposited at 1.33Pa has shown spiky morphology with much lower grain density and porosity than the film deposited at 0.4Pa.•This film deposited at 1.33Pa favoured the formation of active site for OH adsorption and found not suitable for gas sensing.•A higher oxidation state of W (35.9eV) was found in the W-doped ZnO film deposited at 0.4Pa.•This film deposited at 0.4Pa has shown greater gas sensing to NO2 at lower operating temperature most likely due to enhanced free-carrier defects. Pure and W-doped ZnO thin films were obtained using magnetron sputtering at working pressures of 0.4Pa and 1.33Pa. The films were deposited on glass and alumina substrates at room temperature and subsequently annealed at 400°C for 1h in air. The effects of pressure and W-doping on the structure, chemical, optical and electronic properties of the ZnO films for gas sensing were examined. From AFM, the doped film deposited at higher pressure (1.33Pa) has spiky morphology with much lower grain density and porosity compared to the doped film deposited at 0.4Pa. The average gain size and roughness of the annealed films were estimated to be 65nm and 2.2nm, respectively with slightly larger grain size and roughness appeared in the doped films. From XPS the films deposited at 1.33Pa favoured the formation of adsorbed oxygen on the film surface and this has been more pronounced in the doped film which created active sites for OH adsorption. As a consequence the W-doped film deposited at 1.33Pa was found to have lower oxidation state of W (35.1eV) than the doped film deposited at 0.4Pa (35.9eV). Raman spectra indicated that doping modified the properties of the ZnO film and induced free-carrier defects. The transmittance of the samples also reveals an enhanced free-carrier density in the W-doped films. The refractive index of the pure film was also found to increase from 1.7 to 2.2 after W-doping whereas the optical band gap only slightly increased. The W-doped ZnO film deposited at 0.4Pa appeared to have favourable properties for enhanced gas sensing. This film showed significantly higher sensing performance towards 5–10ppm NO2 at lower operating temperature of 150°C most dominantly due to increased free-carrier defects achieved by W-doping.