A new quinazoline functionalized benzimidazole-based fluorogenic chemosensor H₃L is synthesized and fully characterized by conventional techniques including single crystal X-ray analysis. It acts as a highly selective colorimetric and fluorescence sensor for Cu²⁺ ions in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Reaction of H₃L with CuCl₂ forms a mononuclear copper(II) [Cu(Cl)(H₂L)(H₂O)] (H₂L–Cu²⁺) complex which is characterized by conventional techniques and quantum chemical calculations. Electronic absorption and fluorescence titration studies of H₃L with different metal cations show a distinctive recognition only towards Cu²⁺ ions even in the presence of other commonly coexisting ions such as Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Hg²⁺. Moreover, H₂L–Cu²⁺ acts as a metal based highly selective and sensitive chemosensor for S²⁻ ions even in the presence of other commonly coexisting anions such as F⁻, Cl⁻, Br⁻, I⁻, SO₄²⁻, SCN⁻, AcO⁻, H₂PO₄⁻, PO₄³⁻, NO₃⁻, ClO₄⁻, NO₂⁻, HSO₄⁻, HSO₄²⁻, S₂O₃²⁻, S₂O₈²⁻, CN⁻, CO₃²⁻ and HCO₃⁻ in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Quantification analysis indicates that these receptors, H₃L and H₂L–Cu²⁺, can detect the presence of Cu²⁺ and S²⁻ ions at very low concentrations of 1.6 × 10⁻⁹ M and 5.2 × 10⁻⁶ M, respectively. The propensity of H₃L as a bio-imaging fluorescent probe for detection of Cu²⁺ ions and sequential detection of S²⁻ ions by H₂L–Cu²⁺ in Dalton lymphoma (DL) cancer cells is also shown.