Here, we report an organometallic chemistry-assisted method for modification of zinc oxide (ZnO) nanoparticles by tin oxide (SnO2) nanoparticles, providing a novel and efficient approach for preparation of metal oxides-based heterojunction. The SnO2/ZnO heterojunctions were prepared by modification of ZnO nanoparticles with (CH3)2SnCl2 through organometallic chemistry reaction firstly, and subsequently thermal treatment in air atmosphere. The combined characterizations indicate the successful formation of ZnO/SnO2 heterojunctions with controllable surface oxygen vacancy concentrations by optimizing organometallic chemistry reactions. Most importantly, ZnO-Sn-0.75-based NO2 sensor delivers the response of 14.3 toward 0.5 ppm NO2 at 190 °C with response time of 100 s and recovery time of 101 s. It is also found that ZnO-Sn-0.75 sample exhibits better NO2 sensing performances than ZnO nanoparticles and other ZnO-Sn samples (ZnO-Sn-0.50, and ZnO-Sn-1.0). The excellent sensing performances of ZnO-Sn-0.75 are attributed to the synergistic effect n-n heterojunction and controllable surface oxygen species. The present work opens a generalized avenue for facile, cheap and mass production of transition metal oxides-based heterojunctions for various applications.