In the title compound, (CH(6)N(3))(2)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)], the anions lie on crystallographic centres of inversion. The crystal structure adopts a layered structure, stabilized by an extensive network of N-H⋯O and O-H⋯O hydrogen bonds. One H atom of the guanidinium cation does not participate in any strong hydrogen bonds.