Porous conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanocomposite prepared on reduced graphene oxide (RGO) film was used as efficient chemiresistor sensor platform for NO2 detection. The comparable electrical performance between RGO and porous PEDOT nanostructure, the large surface area and opening porous structure of this RGO/porous PEDOT nanocomposite resulted in excellent synergistic effect. The gas sensing performance revealed that, in contrast to bare RGO, the RGO/porous PEDOT exhibited the enhanced sensitivity (2 orders of magnitude) as well as response and recovery performance. As a result of the highly uniform distribution of PEDOT porous network and excellent synergetic effect between RGO and porous PEDOT, this nanocomposite based sensor exhibited higher selectivity to NO2 in contrast to other oxidant analyte gases, e.g., HCl, H2S and SO2.