In the title three-dimensional compound, [CoSm(6)(C(5)H(2)N(2)O(4))(4)(SO(4))(6)(H(2)O)(14)](n), the Co(II) ion is six-coordinated with two O atoms and two N atoms from two imidazole-4,5-dicarboxyl-ate ligands and two coordinated water mol-ecules, giving a slightly distorted octa-hedral geometry. One Sm(III) ion is eight-coordinated in a bicapped trigonal-prismatic coordination geometry by four O atoms from two imidazole-4,5-dicarboxyl-ate ligands, two O atoms from two SO(4) (2-) anions and two coordinated water mol-ecules. The other two Sm(III) ions are nine-coordinated in a tricapped trigonal-prismatic coordination geometry; one of these Sm(III) ions is bonded to four O atoms from two imidazole-4,5-dicarboxyl-ate ligands, three O atoms from three SO(4) (2-) anions and two water O atoms, and the other Sm(III) ion is coordinated by one O atom and one N atom from one imidazole-4,5-dicarboxyl-ate ligand, five O atoms from three SO(4) (2-) anions, as well as two coordinated water mol-ecules. The crystal structure is further stabilized by N-H⋯O, O-H⋯O, and C-H⋯O hydrogen-bonding inter-actions.