Four pincer-type Co (II) complexes of the 2,4-bis (3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine ligand (L) were evaluated for their cytotoxic activities against lung and breast cancer cell lines using cell viability assay. The X-ray single crystal structure of [Co(L)(H2O)(2)Br]Br (1) confirmed the pincer coordination behavior of the ligand L as an N-tridentate chelate. The hexa-coordination environment of Co (II) is completed by one bromide ion completing the equatorial plane of the octahedral structure and two trans water molecules at the axial positions. It crystallized in the monoclinic crystal system and P2(1)/m space group with crystal parameters of a = 11.3170(10) angstrom, b = 7.4613(7) angstrom, c = 12.6917(12) angstrom and beta = 95.927(3)degrees. Based on Hirshfeld analysis, the most dominant contacts are H horizontal ellipsis H (48.8%), Br horizontal ellipsis H (17.6%), H horizontal ellipsis C (11.2%) and O horizontal ellipsis H (10.1%), where the Br horizontal ellipsis H interactions are the most significant. The cytotoxic evaluation of the studied systems indicated that complex [Co(L)(NO3)(2)] (4) has the highest activity against lung (A-549) and breast (MCF-7) cell lines. In contrast, complex [Co(L)(H2O)(3)](ClO4)(2).H2O(3) has the lowest cytotoxic activity against both cell lines.