In the title compound, [Cd(C(6)H(4)O(8)S(2))(C(12)H(8)N(2))(2)(H(2)O)]·H(2)O, each Cd(II) ion is coordinated by four N atoms [Cd-N = 2.310 (7)-2.341 (7) Å] from two 1,10-phenanthroline ligands, one O atom [Cd-O = 2.300 (6) Å] from a 4,5-dihydroxy-benzene-1,3-disulfonate ligand and one aqua O atom [Cd-O = 2.288 (7) Å] in a distorted octa-hedral geometry. The crystal packing exhibits inter-molecular O-H⋯O and C-H⋯O hydrogen bonds and π-π inter-actions evidenced by relatively short distances [3.525 (5)-3.937 (6) Å] between the centroids of the six-membered rings of neighbouring mol-ecules.