In this paper, SnO2 nanoparticles (NPs) decorated reduced graphene oxide hybrids with abundant vacancies (designated as SnO2-RGO-OVs) have been successfully prepared by a combined hydrothermal synthesis and chemical solution deposition method. It is found that high density SnO2 NPs with the size of 3–5 nm are uniformly distributed on the surface of RGO nanosheets. Most importantly, SnO2-RGO-OVs hybrids exhibit excellent room-temperature NO2 sensing properties with the low detection limit of 50 ppb. When SnO2-RGO-OVs-based sensor was exposed to 1 ppm NO2, the response is 3.80 and response time and recovery time are 14 s and 190 s, respectively. These sensing performances are superior to those of most reported room-temperature NO2 sensors based on RGO-based materials and other materials. The excellent sensing performances of SnO2-RGO-OVs hybrids can be attributed to their specific structure, e.g., RGO that could facilitate transferring carriers during sensing progress, and abundant OVs that could facilitate adsorption of more NO2 molecules onto SnO2 NPs in SnO2-RGO-OVs hybrids.