Two water-soluble ternary copper(II) complexes of [Cu(L)Cl](ClO 4 ) (1) and [Cu(L)Br 2 ] (2) (L=(2-((quinolin-8-ylimino)methyl)pyridine)) were prepared and characterized by various physico-chemical techniques. Both 1 and 2 were structurally characterized by X-ray crystallography. The crystal structures show the presence of a distorted square-pyramidal CuN 3 Cl 2 (1) or CuN 3 Br 2 (2) geometry in which Schiff-base L acts as a neutral tridentate ligand. Both complexes present intermolecular π–π stacking interactions between quinoline and pyridine rings. The interaction of two complexes with CT-DNA (calf thymus-DNA) and BSA (bovine serum albumin) was studied by means of various spectroscopy methods, which revealed that 1 and 2 could interact with CT-DNA through intercalation mode, and could quench the intrinsic fluorescence of BSA in a static quenching process. Furthermore, the competition experiment using Hoechst 33258 indicated that two complexes may bind to CT-DNA by a minor groove. DNA cleavage experiments indicate that the complexes exhibit efficient DNA cleavage activities without any external agents, and hydroxyl radical (HO) and singlet oxygen ( 1 O 2 ) may serve as the major cleavage active species. Notably, the in vitro cytotoxicity of the complexes on three human tumor cells lines (HeLa, MCF-7, and A549) demonstrates that two compounds have broad-spectrum antitumor activity with quite low IC 50 ranges of 0.43–1.85μM. Based on the cell cycle experiments, 1 and 2 could delay or inhibit cell cycle progression through the S phase.