We report the biological activity of the new Schiff base ligand H 2 L (H 2 L = 6,6'-((1E,11E)-5,8-dioxa-2,11-diazadodeca-1,11-diene-1,12-diyl)bis(2,4-dichlorophenol)), its derived metal(II) complexes [Cu(L)] (1), [Co(L)] (2), [Ni(L)] (3) and [Zn(L)] (4), alongwith their structural characterizations by using various analytical and spectroscopic techniques. Single crystal XRD studies suggested that the prepared metal(II) complexes adopted a distorted tetrahedral geometry. The 1 H NMR and FTIR data concluded that the Schiff base ligand H 2 L acts as a tetra-dentate ligand coordinating with metal(II) ions through the oxygen atom of the phenolic group and nitrogen atom of the azomethine group. Complexes 1 and 4 were found to be efficient in bringing about antimicrobial activities. The proposed mechanism of their antimicrobial activities has been discussed. 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay showed the remarkable cytotoxicity of complex 1 (IC 50 = 19 ± 1.1 μg/mL) on human breast cancer MCF-7 cells than Schiff base ligand H 2 L and complexes 2–4. Moreover, AO/EB staining assay revealed cell death due to apoptosis in MCF-7 cells and the generation of ROS by the Schiff base ligand H 2 L and its derived metal(II) complexes 1–4 may be a possible cause for their cytotoxic activity. © 2019 Elsevier B.V.