A novel copper(II) coordination polymer, poly[[[aquacopper(II)]-mu3-2,2'-bipyridyl-3,3'-dicarboxylato-kappa4N,N':O:O'] dihydrate], {[Cu(C12H6N2O4)(H2O)].2H2O}n, was obtained by the reaction of CuCl2.2H2O and 2,2'-bipyridyl-3,3'-dicarboxylic acid (H2L) in water. In the molecule, each Cu(II) atom is five-coordinated and lies at the centre of a square-pyramidal basal plane, bridged by three L ligands to form a two-dimensional (4,4)-network. Each L moiety acts as a bridging tetradentate ligand, coordinating to three Cu(II) atoms through its two aromatic N atoms and two O atoms of the two carboxyl groups. The two-dimensional square-grid sheets superimpose in an off-set fashion through the inorganic water layer.