In the asymmetric unit of the title coordination polymer, {[CoNa(C(10)H(12)N(2)O(8))(H(2)O)(2)]·2H(2)O}(n), the Co(II) ion is coord-inated in a distorted octa-hedral environment, defined by two N atoms and four carboxyl-ate O atoms. Two Co(II) ions and two 2-({2-[(1,2-dicarboxyl-atoeth-yl)amino]-eth-yl}amino)-butane-dio-ate (EDDS) ligands form a dimeric complex dianion [Co(2)(EDDS)(2)]. These dimeric units are connected via Na(+) ions, forming a three-dimensional polymeric structure. In the crystal, the ligand N-H groups and the coordinated and solvent water mol-ecules are involved in inter-molecular N-H⋯O and O-H⋯O hydrogen bonding, reinforcing the three-dimensional polymeric structure.