2-Hydroxy-naphthaldeazine (HNA), synthesized readily via one-step condensation from 3-hydroxy-2-naphthaldehyde and hydrazine monohydrate, behaves as “turn-on” fluorescent sensing of CN−selectively. The sensing mechanism was ascribed to the dual influence of hydrogen bonds and aggregation-induced emission, coming from the interactions of HNA and CN−. The speculation was partially supported by fluorescence emission spectra, UV–vis spectrum, 1H NMR titration experiments and further particle size analysis