The title complex, [CuNi(C(13)H(16)N(3)O(3))(C(10)H(8)N(2))(2)(H(2)O)]ClO(4), has a cis-oxamide-bridged heterobinuclear cation, with a Cu···Ni separation of 5.3297 (6) Å, counterbalanced by a disordered perchlorate anion. The Cu(II) and Ni(II) cations are located in square-pyramidal and octahedral coordination environments, respectively. The complex molecules are assembled into a three-dimensional supramolecular structure through hydrogen bonds and π-π stacking interactions. The influence of the two types of metal cation on the supramolecular structure is discussed.