Hypochlorite plays a critical role in various physiological processes and is involved in many diseases. Thus, real-time, rapid, and accurate monitoring of hypochlorite has important medical and physiological significance. Herein, a novel coumarin–pyridine derivative (CPD) probe was designed and synthesized, which exhibited fantastic advantages, such as a rapid response (within 10 s), naked eye recognition, large Stokes shift (185 nm), dual-channel detection, and high selectivity and sensitivity toward OCl⁻ (detection limit 0.012 μM, S/N = 3). Furthermore, the current CPD probe was successfully used to image OCl⁻ in the mitochondria of both A549 cells and zebrafish, which further demonstrated its suitability for practical applications in biological systems.