The title complex, {[Co(2)(C(9)H(4)N(2)O(4))(2)(H(2)O)(4)]·3H(2)O}(n), was synthesized hydro-thermally. The unique Co(II) ion is coordin-ated in a distorted octa-hedral coordination environment by two water mol-ecules and three symmetry-related 1H-benzimid-azole-5,6-dicarboxyl-ate (Hbidc) ligands. The Hbidc ligands coordinate via a bis-chelating and mono-chelating carboxyl-ate group and by an imidazole group N atom, bridging the Co(II) ions and forming an extended two-dimensional structure in the ab plane. In the crystal structure, inter-molecular N-H⋯O and O-H⋯O hydrogen bonds connect complex and solvent water mol-ecules, forming a three-dimensional supermolecular network. One of the solvent water mol-ecules lies on a twofold rotation axis.