n this study, two complexes (one precursor and one new) were synthesized from 1,10- phenanthroline alone as [Co(phen)2(H2O)2]Cl2 and from both 1,10-phenanthroline and chrysin as [Co(phen)(chry)]Cl2.1.25H2O. The synthesis was checked using physicochemical techniques (solubility tests, molar conductivity, melting point, chloride test, metal determination and TGA) and spectroscopic techniques (UV-Vis and FT-IR). Based on the above data a tetrahedral geometry were proposed for both complexes. The In vitro antibacterial activities of the two metal complexes were tested against one Gram-positive Staphylococcus aureus (S. aureus) and one Gram-negative Escherichia coli (E.coli) bacteria using the disc diffusion method. Cobalt(II) complexes were active against Gram-negative bacteria (Escherichia coli) even though well known for their activity against Gram-positive bacteria. However the result shows the two complexes were less active compared to the commercial antibiotic drug tetracycline in all bacteria strains. Keywords: Co(II) complexes, 1,1 0-phenanthroline, Chrysin, antibacterial activity