Hypochlorite (ClO-) is one of the most important reactive oxygen species but using a BL probe for its selective detection (or imaging) still remains challenging. Herein, we report a latent BL probe benzoylhydrazine luciferin (1) for highly selective detection of ClO- in vitro and imaging ClO- in living cells and tumors. In vitro tests indicated that 1 could be applied for highly selective detection of ClO- within the range of 0-62.5 μM with a limit of detection of 0.705 μM. Using these unique features of 1, we successfully applied it to image ClO- in living cells and tumors. We envision that probe 1 might be applied to elucidate the biological roles of ClO- in wider physiological and pathological processes in the near future.