A highly selective and sensitive boron-dipyrromethene (BODIPY) based fluorescent probe (Bodipy-Hy) for the detection of hypochlorous acid (HOCl) was designed and easily synthesized by the condensation reaction (CN) of BODIPY aldehyde (BODIPY-AL) and hydrazine hydrate, which contain a newer group compared with other similar probes. With the specific HOCl-promoted oxidation grade of the CN bond increasing, the fluorescence intensity of Bodipy-Hy gradually increased more than 11-fold. And the fluorescent quantum yield enhances from 0.06 to 0.62. A linear increase of fluorescence intensity could be observed under the optimum conditions with increasing HOCl concentration over a wide linear range 0–22.5 μM, then a lower detection limit of 56 nM based on 3 × δ_blank/k was obtained. Moreover, the probe can also be successfully applied to imaging HOCl in living cells with low cytotoxicity.