A bioreductant-resistant 'turn-on' chemodosimetric fluorescent probe Mito-1 has been developed for the detection of mitochondrial HNO in live cells. Mito-1 enables the detection of HNO as low as ∼18 nM. It has the capability to detect both exogenous and endogenous mitochondrial HNO formations in cellular milieus by providing fluorescence images. Its two-photon imaging ability fosters its use as a noninvasive imaging tool for the detection of mitochondrial nitroxyl.