A novel strategy for developing a hypochlorite fluorescent probe by exploiting the ortho-vinylhydropyridine-assisted amido-to-nitroso oxidation reaction is presented. The designed 1,8-naphthalimide-based derivative (1a) is employed to monitor and identify trace amounts of ClO⁻ with the advantage of fast response (within 1.2 seconds, LOD = 36.0 nM), good selectivity, and high sensitivity in solution and living cells.