Conducting polymers (CPs) have attracted wide interest for application in chemical gas sensors due to their versatile nanostructure, easy synthesis, and good environmental stability, as well as a superior sensing capability at room temperature. Polyaniline, polypyrrole polythiophene and their derivatives are among the most extensively used CPs for gas sensing applications. Due to the prominent structure and morphology effects, a variety of means have been developed to manipulate nanostructures of CPs in order to explore the structure-property relationships in gas sensing. Hybrid materials incorporating CPs and various inorganic components including nanocarbons (graphene and carbon nanotubes), metal nanoparticles, and metal oxide nanostructures also demonstrate great potential for advanced sensors due to the enhanced surface adsorption, modulation of redox properties and electronic interactions. In light of these advances, this review intends to critically focus on the progress in synthesis protocols, structure engineering and hybridization design of CPs to highlight the unique sensing functions, strategies and perspectives of CPs for future gas sensors.