The title compound, [Co(C(12)H(8)N(2))(H(2)O)(4)](2)[Co(H(2)O)(6)](C(11)H(7)O(8))(2)·4H(2)O, was obtanied by the reaction of cobalt acetate with 3,5-bis-(carb-oxy-meth-oxy)benzoic acid and 1,10-phenanthroline. The asymmetric unit contains one tetra-aqua-(1,10-phenanthroline)cobalt(II) cation, one half of a hexa-aqua-cobalt(II) cation that is completed by inversion symmetry, one 3,5-bis-(carboxyl-atometh-oxy)benzoate trianion and two lattice water mol-ecules. The two Co(II) atoms each show a slightly distorted octa-hedral coordination (CoO(6) and CoO(4)N(2)). The cations, anions and lattice water mol-ecules are linked by an intricate network of O-H⋯O hydrogen bonds into a three-dimensional structure.