A new probe (RosN₃), which displayed excellent selectivity to H₂S in mixed aqueous media, was synthesized. This method employed the H₂S-mediated reduction of azides to amines, resulting in fluorescence quenching. The probe exhibited high H₂S selectivity over other common anions and biothiols. The detection limit was measured to be 0.25 μM. Furthermore, the live cell imaging results demonstrated its potential for practical application in biological systems.