ZnO nanoparticles or nanosheets have been in-situ grown on the substrate via a facile green approach featured with the hydrothermal treatment of electrospun nanofibers comprising polyvinyl alcohol and zinc acetate. The nanohybrids of ZnO with polypyrrole (PPy) were fabricated by the vapor phase polymerization of pyrrole on the surface of as-prepared nanostructured ZnO. The resulting nanohybrids were characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, field emission scanning electron microscopy and high-resolution transmission electron microscopy and Brunauer-Emmett-Teller surface area measurements. Moreover, the electrical responses of the nanohybrids to NH3 have been examined at room temperature. It was found that the nanohybrids revealed much higher response magnitude than either of the constituent component. Additionally, the morphology of ZnO affected the response magnitude of PPy/ZnO nanohybrids. The hybrids of ZnO nanosheets with PPy showed wide sensing range (0.5-200 ppm), very high response magnitude (relative resistance change of similar to 20% towards 0.5 ppm of NH3), good repeatability and selectivity. Attempts have been made to explore the gas sensing mechanism of the PPy/ZnO nanohybrids. (C) 2016 Elsevier B.V. All rights reserved.