A one-dimensional chain cobalt(II) coordination polymer with 2,4,6-trimethyl-benzoic acid, 1,10-phenanthroline and cobalt perchlorate anhydrous has been synthesized in the solvent mixture of water/methanol and characterized. Crystal data for this complex: tetragonal, space group I4(I), a = 2.0356(2), c = 1.3779(3) nm, V = 5.7096(15) nm(3), M-r = 581.51, mu(MoK alpha) = 0.644, D-c = 1.353 g/cm(3), Z = 8, F(000) = 2424, final S = 1.005, R = 0.0404 and wR = 0.0865. The crystal structure shows that the cobalt ion is coordinated with two nitrogen atoms of one 1,10-phenanthroline molecule, three oxygen atoms from three 2,4,6-trimethylbenzoic acid molecules and one water molecule, giving a distorted octahedral coordination geometry. The result of TG analysis indicates that the title complex is stable till 200 degrees C.