In the title compound, [Cd(C(6)H(6)N(2)O)(2)(H(2)O)(4)](C(10)H(8)O(6)S(2)), the Cd(II) ion is located on a crystallographic inversion centre. An octa-hedral coordination geometry is defined by four water mol-ecules in one plane, and two trans N-atom donors of the nicotinamide ligands. The biphenyl-4,4'-disulfonate anion also lies on a crystallographic inversion centre. In the crystal structure, the complex cations are connected to the counter-anions via N-H⋯O and O-H⋯O hydrogen bonds, forming a three-dimensional network.