Flexible gas sensor devices comprised of heating and transducing elements are produced by directly integrating multilayer polymeric-based platforms and highly crystalline semiconducting metal oxide nanostructures grown via vapour-phase method, as main improvement over other methods for fabricating flexible gas sensors. Thermal simulations and characterizations of the heating element demonstrate these devices provide uniform temperature distribution at the sensing active area, and the electrical properties of the sensing film and electrodes indicate the networked-nanostructures are ohmically connected. Validation of the sensing device shows repeatable and satisfactory responses towards ethanol, demonstrating this fabrication method, with potential in a cost effective production for large-scale applications, is an attractive route for developing next generation of gas sensing devices provided of flexibility and functionality.