An efficient and highly selective dihydrazone based fluorescent probe N′,N′–bis((2–hydroxynaphthalen–1–yl)methylene)malonohydrazide (H₂nmh), has been synthesized for selective detection of Al³⁺ ions and characterized by different physico–chemical and spectroscopic techniques. The probe shows an enhanced fluorescence in the presence of Al³⁺ ions in ethanol–water (2:3 v/v) solution which is not observed in the presence of other cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺ and Hg²⁺). The binding modes of H₂nmh with Al³⁺ were studied by UV–vis, fluorescence and ¹H NMR titrations. The probe act as dibasic hexa–dentate ligand and interacts with two Al³⁺ ions with a binding constant K_B = 5.74 × 10⁹ M⁻¹ and detection limit 5.78 × 10⁻⁸ M. Detailed insights of probe–metal interaction mechanism were studied by mean of density functional theory (DFT) as well as time dependent–DFT calculation. MTT assay on live MCF–7 cells has been performed to evaluate the cytotoxicity of the probe which suggests viability of the probe to MCF–7 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicates that the accumulation of Al³⁺ in the cytoplasm of cells can be detected by H₂nmh.