In the title mixed-ligand metal–organic polymeric complex [Cd(C14H8O6S)(C16H16N2)(H2O)]n, the asymmetric unit contains a crystallographically unique CdII atom, one doubly deprotonated 4,4′-sulfonyldibenzoic acid ligand (H2SDBA), one 3,4,7,8-tetramethyl-1,10-phenanthroline (TMPHEN) molecule and one water molecule. Each CdII centre is coordinated by two N atoms from the chelating TMPHEN ligand, three O atoms from monodentate carboxylate groups of three different SDBA2− ligands and one O atom from a coordinated water molecule, giving a distorted CdN2O4 octahedral geometry. Single-crystal X-ray diffraction analysis reveals that the compound is a one-dimensional double-chain polymer containing 28-membered rings based on Cd2O2 clusters, with a Cd...Cd separation of 3.6889 (4) Å. These chains are linked by O—H...O and C—H...O hydrogen bonds to form a three-dimensional supramolecular framework. The framework is reinforced by π–π and C—O...π interactions.