In this work, we present a new reaction-based luminogenic probe with dual functions: a highly selective sensor for both in vitro H2S sensing and in vivo H2S imaging in living zebrafish, and a luminescent agent for imaging hypoxic cells. The mechanism of this platform is based on the reduction of the nitro group in the iridium(III) complex to an amino group, which turns on its luminescence. Complex 1 exhibited a linear range of detection for H2S from 0 to 170 M with a detection limit of 4.35 M. Complex 1 also shows the ability to detect H2S in HeLa cells and in living zebrafish. Meanwhile, complex 1 is capable of discriminating hypoxic from normoxic cells, and shows potential for monitoring hypoxia in zebrafish model.