ABSTRACT Cobalt can bind to a range of biomolecules forming complexes that are suitable for use in various biological applications. Different ligands could be used to tune the properties of cobalt compounds and designing coordination compounds. Ligand tailoring with therapeutic abilities has become a fascinating field. From this perispective, cobalt(II) coordination compounds of Formula [Co(L1)2(H2O)2]Cl2, [Co(L1(H2O)4]Cl2, [CoL1L2(H2O)2], 2Na[CoL1(L2)2], [Co(L1)2L2], [CoL1(L3)(H2O)3]Cl2 and[CoL1L2L3(H2O)] (L1=1,10-phenanthroline, L2=Oxalate, L3=Adenine) were synthesized and characterized using spectroscopy (FT-IR ,ICP-OES, ESI MS),halide test, solubility test, melting point, and electrolytic conductivity. The results suggested that the ligands are coordinated with the metal ion. The complexes containing oxalate are found either partially soluble or completely insoluble in most of the common solvents including water. The complexes were tested for antibacterial activity against two Gram positive (Staphylococcus aureus and Streptococcus pyogenes) and two Gram negative (Escherichia coli and Klebsiella pneumonia) bacteria. The result disclosed that the completely and partially soluble complexes to be active against all the tested bacteria. Thus, after passing the in vivo test, these complexes could be considered medicines for problems caused by these bacteria. Keywords: Co (II) mixed ligand complexes, Oxalate, 1, 10-phenanthroline, Adenine, Antibacteriallacitivty