Very few different reducible chemical functionalities have been used in the design of reduction‐based fluorescent probes. Reported herein is a nitroso‐based fluorescence turn‐on probe that displays an almost instantaneous and strong fluorescence response towards hydrogen sulfide. Since the recent discovery that hydrogen sulfide plays a key role in many biological and physiological processes, the development of novel methods to efficiently detect this molecule has become an intensive field of research. In this context, fluorimetric strategies have become one of the methods of choice. However, very few different reducible chemical functionalities have been successfully used in the design of reduction‐based probes for the fluorescence detection of hydrogen sulfide. Reported herein is the first nitroso‐based fluorescence turn‐on probe that displays an almost instantaneous and strong fluorescence response towards hydrogen sulfide. A comparative study carried out with the hydroxylamino‐based probe analogue showed a significant difference in fluorescence response.