The title compound, [Co(2)(C(9)H(4)N(2)O(4))(2)(H(2)O)(4)](n), is a one-dimensional polymeric complex with bridging 1H-benzimidazole-5,6-dicarboxyl-ate and aqua ligands. The Co(II) cation has an octa-hedral coordination environment provided by an NO(5) donor set. Adjacent polymeric chains extended along the [100] direction are linked by O-H⋯O and N-H⋯O hydrogen bonds, generating a three-dimensional network.