In the title coordination complex, {[Cd(C10H8O6)(H2O)2]·H2O}n the CdII atom is seven-coordinated in a distorted penta­gonal–bipyramidal geometry, the penta­gonal plane comprising four O-atom donors from the 2,2′-(1,2-phenyl­enedi­oxy)diacetate chelate ligand together with a bridging carboxyl­ate O-atom donor, with the axial sites occupied by two water mol­ecules. The resulting helical chains extend along the b axis and are inter­connected by extensive O—H⋯O hydrogen-bonding inter­actions, which also involve the water mol­ecule of solvation, giving a three-dimensional structure.