A hydroxybenzohydrazide-based Schiff base ligand was conveniently synthesized. Upon addition of Zn(2+) cations, the ligand exhibited a high tendency to form a binuclear structure with a 2 : 2 ligand-to-zinc ratio, which was accompanied by a large fluorescence turn-on (λem = 507 nm, ϕfl≈ 0.28). The reactivity of the zinc complex was examined using different phosphate anions, which reveals a higher response to acid pyrophosphate anions. Detailed spectroscopic studies show that the pyrophosphate response is based on the ligand displacement mechanism.