The microstructures of metal oxide-modified reduced graphene oxide (RGO) are expected to significantly affect room-temperature (RT) gas sensing properties, where the microstructures are dependent on the synthesis methods. Herein, we demonstrate the effect of microstructures on RT NO₂ sensing properties by taking typical SnO₂ nanoparticles (NPs) embellished RGO (SnO₂NPs-RGO) hybrids as examples. The samples were synthesized by growing SnO₂ NPs on RGO through hydrothermal reduction (SnO₂ NPs-RGO-PR), which display the advantages such as high reactivity of the SnO₂ surface with NO₂, more oxygen vacancies (O_V) and chemisorbed oxygen (O_C), close contact between SnO₂ NPs and RGO, and large surface area, compared to the samples prepared by one-pot hydrothermal synthesis from Sn⁴⁺ and GO (SnO₂ NPs-RGO-IS), and the assembly of SnO₂ NPs on RGO (SnO₂ NPs-RGO-SA). As expected, the SnO₂ NPs-RGO-PR-based sensor presents high sensitivity towards 5 ppm NO₂ (65.5%), but 35.0% for the SnO₂NPs-RGO-IS-based sensor and 32.8% for the SnO₂ NPs-RGO-SA-based sensor at RT. Meanwhile, the corresponding response time and recovery time calculated by achieving 90% of the current change of the SnO₂ NPs-RGO-PR-based sensor for exposure to NO₂ is 12 s and to air is 17 s, respectively, whereas 74/42 s for the SnO₂ NPs-RGO-IS-based sensor and 77/90 s for the SnO₂ NPs-RGO-SA-based sensor. The results can prove the tailoring sensing behavior of the gas sensor according to different structures of materials.