In the title complex, {[Co(C(10)H(8)N(2))(H(2)O)(4)](C(11)H(10)O(5))}(n), the unique Co(II) ion lies on an inversion center and is coordinated by two N atoms from two 4,4'-bipyridine ligands and four O atoms from four water mol-ecules in a slightly distorted octa-hedral coordination geometry. The 4,4'-bipyridine ligands bridge Co(II) ions into a one-dimensional chain structure. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link cations and anions into a three-dimensional network. The dianions are completely disordered about an inversion center.