In this work, we have reported a novel NO2 sensor using molybdenum disulfide nanoparticles (MoS2 NPs) decorated RGO (MoS2-RGO) hybrids as sensing materials, where MoS2-RGO hybrids were prepared by a two-step wet-chemical method. Firstly, MoS2 NPs prepared by modified liquid exfoliation method from bulky MoS2 powder. Then, MoS2-RGO hybrids were obtained by self-assembly of MoS2 NPs and GO nanosheets, followed by a facile hydrothermal treatment progress. The combined characterizations indicate that MoS2 NPs with the size of 3–5 nm are uniformly dispersed on RGO nanosheets. Most importantly, the sensor based on MoS2-RGO hybrids could detect NO2at room temperature. To further improve sensing performances, especially response and recovery rate, sensing properties are further examined by increasing the operation temperature to 160 °C. It is notably seen that MoS2-RGO-based NO2 sensor not only shows improved sensitivity to NO2 compared to pure RGO-based sensor, but also exhibits fast response and recovery characteristics (response time and recovery time are 8 s and 20 s toward 3 ppm NO2). This work paves a new way for application of MoS2 and RGO in chemical sensors, providing an effective method for fabrication of NO2 sensors with high sensitivity and fast response/recovery rate.