Molybdenum disulfide (MoS2) has sparked immense interests as a novel gas sensing material due to its inherent layered structure and large surface-to-volume ratio. However, the obstacles of insufficient sensitivity and poor recoverability for MoS2-based gas sensors need to be resolved for the further applications. Herein, we report the construction of MoS2 nanosheets based p-n heterostructures for the purposes of achieving excellent NO2 detection at room temperature. After functionalized with fin oxide (SnO2) nanoparticles, the optimal MoS2/SnO2 heterostructure-based gas sensor exhibits a response of 18.7 to 5 ppm nitrogen dioxide (NO2), an outstanding selectivity compared with other gases, and an excellent long-term stability for 4 weeks. The enhanced sensing performance of MoS2/SnO2 heterostructures can be ascribed to the unique 2D/0D nanostructures and the formation of numerous p-n heterojunctions. Therefore, construction of p-n heterostructures provides a versatile solution to overcome the sensing issues of MoS2-based gas sensors and also paves a new way for others room temperature sensor applications.