In the title complex, [BaCd(C(3)H(2)O(4))(2)(H(2)O)(4)](n), the Ba(II) atoms, located on crystallographic twofold axes, adopt slightly distorted square-anti-prismatic coordination geometries, while the Cd(II) atoms, which lie on crystallographic centres of symmetry, have a distorted octa-hedral coordination. Each malonate dianion binds two different Cd(II) atoms and two different Ba(II) atoms. This connectivity generates alternating layers along [100] in the structure, with one type containing Cd(II) cations and malonate dianions, while the other is primarily composed of Ba(II) ions and coordinated water mol-ecules. The water mol-ecules also participate in extensive O-H⋯O hydrogen bonding.