Four Co(II) complexes of hexamethylenetetramine (HMTA), [Co(HMTA)2(NO3)2(H2O)2], [Co(HMTA)(SCN)2(H2O)3], [Co2(HMTA)(N3)3(H2O)5] and [Co(HMTA)(DCA)2(H2O)]. H2O have been synthesized and were characterized by physico-chemical and spectroscopic methods. The results suggest that these complexes are octahedral, stable in air and non-hygroscopic as opposed to the starting metal salt. The ligands, metal salt and the complexes were also evaluated for their antimicrobial activities in vitro against seven pathogens.