A series of structurally related Ni(II), Cu(II) and Zn(II) 5,5-diethylbarbiturate (barb) complexes with bis(2-pyridylmethyl) amine (1-3) and terpyridine (4-6) were synthesized and characterized using elemental analysis, UV-vis, IR, and ESI-MS. Single-crystal X-ray diffraction analysis showed that all complexes are mononuclear. Interactions of the complexes with DNA and protein were studied in detail using experimental and molecular docking techniques, indicating that all the complexes bind to DNA, exhibiting non-covalent binding specificity for G/C and A/T rich regions via a partial intercalative/groove binding mode, and effectively quench the intrinsic fluorescence of BSA through intermolecular interactions. The Cu(II) complexes (2 and 5) displayed a moderate antioxidant activity. In vitro cytotoxicity of 1-6 towards four cancer cell lines was evaluated and compared with that of cisplatin. 2 and 5 showed potent and selective cytotoxic activity against MCF-7 cells, suggesting that the DNA/BSA binding affinity of both complexes correlates with their growth inhibition effects. Furthermore, both complexes induced apoptosis on MCF-7 cells as revealed using flow cytometry analysis. The cytotoxicity and apoptosis induction exerted by 2 and 5 were associated with production of reactive oxygen species (ROS).