An enhanced spectrofluorimetric method for highly selective and sensitive determination of nmol L⁻¹ of hypochlorite has been performed. In alkaline medium, ferrocyanide was specifically oxidized by hypochlorite to form ferricyanide, which further reacted with non-fluorescent thiamine, resulting in the formation of blue fluorescent thiochrome. Notably, the fluorescence intensities were positively correlated with the concentration of hypochlorite over the range of 0.02–12.5 μmol L⁻¹. The detection limit was 6.1 nmol L⁻¹, which was lower than for most of the recently published methods. The experimental conditions were optimized and effects of coexisting substances were evaluated and the results showed excellent priority since a certain amount of other anions, including ClO₃⁻, BrO₃⁻, IO₃⁻, Cr₂O₇²⁻ and other acid radicals, would not interfere with the measurement.