The crystal structure determination of the title compound, [Ni(C6H15NO3)(2)](C4O4), is reported; the squarate dianion is located on an inversion centre and a supramolecular architecture is formed. All the O atoms of the squarate dianion are involved in hydrogen bonding and connect two centrosymmetric nickel triethanolamine complex cations through two symmetry-related hydrogen bonds. There is also a hydrogen-bond interaction between the free hydroxyl O atom of the complex canon and one of the O atoms of the squarate dianion. All these hydrogen bonds link the molecular units in chains. The inter-chain packing is formed by van der Waals forces.