The title compound, [Co(C(14)H(6)N(2)O(4))(H(2)O)(3)]·2H(2)O, has two-fold crystallographic symmetry. The Co(II) atom is in a distorted penta-gonal-bipyramidal coordination environment with two N atoms and two O atoms from a tetradentate 1,10-phenanthroline-2,9-dicarboxyl-ate ligand and one O atom from a water mol-ecule forming the penta-gonal plane, and two O atoms from two water mol-ecules occupying axial positions. In the crystal, adjacent mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network.