In this paper, we demonstrate room-temperature NO2 gas sensors using Pd nanoparticles (NPs) and SnO2 NPs decorated reduced graphene oxide (Pd-SnO2-RGO) hybrids as sensing materials. It is found that ultrafine Pd NPs and SnO2 NPs with particle sizes of 3-5 nm are attached to RGO nanosheets. Compared to SnO2-RGO hybrids, the sensor based on Pd-SnO2-RGO hybrids exhibited higher sensitivity at room temperature, where the response to 1 ppm NO2 was 3.92 with the response time and recovery time being 13 s and 105 s. Moreover, such sensor exhibited excellent selectivity, and low detection limit (50 ppb). In addition to high transport capability of RGO as well as excellent NO2adsorption ability derived from ultrafine SnO2 NPs and Pd NPs, the superior sensing performances of the hybrids were attributed to the synergetic effect of Pd NPs, SnO2 NPs and RGO. Particularly, the excellent sensing performances were related to high conductivity and catalytic activity of Pd NPs. Finally, the sensing mechanism for NO2 sensing and the reason for enhanced sensing performances by introduction of Pd NPs are also discussed.