A new thiazole-based ligand was prepared and investigated then used to preparing its Co(II) and Cu(II) complexes. All available analytical (CHN analysis & TGA) and spectral (IR, UV–Vis, 1H NMR, Mass, SEM, XRD & EDX) techniques were applied to elucidate the chemical formulae of new compounds. The ligand behaved as a neutral tetradentate towards binuclear metal ions in the two complex via N-H, two C = N and C-S groups. A tetrahedral geometry was suggested for Co(II) complex according to 4A2(F)→4T1(F)(ʋ3) transition at 15,873 cm−1. While, a square-planer geometry was suggested for Cu(II) complex according to 2B1g →2B2g (ʋ1) and 2B1g → 2Eg transitions. The magnetic moment values of the two complexes were appeared lower than the normal values, due to binuclear presence minimized electron spinning. The mass spectra of the complexes recorded their molecular ion peaks that match to the molecular formula after expel of crystal water molecules. A conductometry study was executed for the complex formed from nano-sized CuCl2 and the ligand in solution to extract the association and formation constants as well as the M : L molar ratio. The stereo structures of the ligand and its binuclear complexes were optimized by DFT method under valence double-zeta basis set. The distribution of N(1)-N(10), C(11)-S(12) and C(15)-N(13) groups is suitable for their coordination with the two metal ions without bond strain. The in vitro assay was performed for the new compounds against HePG2, PC3 and MCF-7 cancer cell lines. The two complexes exhibited high toxicity against breast cancer cells. This result was confirmed interestingly via in silico ways as pharmacophore query and MOE-docking. The interaction parameters and docking patterns reflect the superiority of Co(II) and Cu(II) complexes in controlling breast cancer cell which agree with that obtained in vitro.