2-Dimensional semiconductor SnS₂ has emerged as one of the most prospective candidates for chemoresistive gas sensor applications due to its outstanding gas sensing performance. Herein, we propose the room temperature nitrogen dioxide (NO₂) sensing of SnS₂ nanoflowers (NFs) enabled by visible light activation. SnS₂ NFs were successfully prepared by solvothermal synthesis with abundant edge sites. The high absorbance in the visible light region triggered the generation of charge carriers resulting in decreased resistance and enhanced gas sensing characteristics. Even under red light and green light with low photon energy, the room temperature NO₂ sensing performance was improved. The highest NO₂ sensing performance was accomplished under blue light, including the highest response, excellent selectivity towards NO₂ and an extremely low detection limit. Moreover, the sensor exhibited reliable gas sensing performance in humid conditions and maintained its properties after long-term relaxation. Taking advantage of surface properties, optical properties and gas sensing properties, a light-activated SnS₂ NF based gas sensor is anticipated to further develop SnS₂ nanostructures for use in an electronic nose.