To elucidate the complex role of biological H2S and study the mitochondrial damage and some related diseases, effective methods for visualization of H2S in mitochondria and in vivo are urgently needed. In this contribution, a novel near-infrared mitochondria-targetable fluorescence probe MI-H2S for H2S detection was developed. MI-H2S shows rapid detection ability for H2S in pure aqueous solution and outputs a highly selective and sensitive fluorescence-on signal at 663 nm with a large Stokes shift of 141 nm. Bioimaging experiments revealed that the probe has good mitochondrial-targeting ability and high-contrast imaging ability for detecting H2S in living systems. The probe also showed great potential in the detection of H2S during inflammation. All of the results demonstrate that MI-H2S can be applied as an effective probe for the visualization and study of H2S in mitochondria and in vivo.