In the title compound, {[Cd(C(8)H(4)O(4))(C(11)H(6)N(2)O)(H(2)O)(3)]·2H(2)O}(n), the Cd(II) atom is seven-coordinated by two N atoms from the phenanthroline-derived 4,5-diaza-fluorene-9-one ligand, two O atoms from one bidentate benzene-1,3-dicarboxyl-ate ligand and three O atoms from the three water mol-ecules in a distorted penta-gonal-bipyramidal arrangement. Moreover, there are two dissociative water mol-ecules in each unit. Neighbouring units inter-act through π-π inter-actions [centroid-centroid distances = 3.325 (3) and 3.358 (4) Å] and O-H⋯O hydrogen-bonding, resulting in a two-dimensional network extending parallel to (001).