The asymmetric unit in the title compound, {[Cd(2)(C(4)H(4)O(6))(SO(4))(H(2)O)(5)].3H(2)O}(n), is composed of two cadmium cations, one (R,R)-tartrate and one sulfate anion, five aqua ligands and three solvent water molecules. One of the cadmium ions is coordinated in an octahedral environment, whereas the second is surrounded by seven O atoms in a pentagonal-bipyramidal geometry. Both types of coordination polyhedra form two sets of perpendicular non-intersecting polymeric chains. CdO(6) octahedra share two corners, while CdO(7) units are joined by a bridging carboxylate group. An extensive hydrogen-bond pattern involving all of the OH groups contributes to the stabilization of the structure.