In the novel transition metal isothiocyanate complex of N-(2-hydroxyethyl)ethylenediamine (hydet-en) with copper, [Cu(NCS)2(C4H12N2O)], the Cu atom lies in a distorted square-pyramidal environment, coordinated by four N atoms in the basal plane and an apical O atom. The hydet-en ligand is N,N,O-tridentate, in contrast to the disposition in previously studied complexes, while the isothiocyanate ions act as N-atom donor ligands. The monomeric units are linked to one another by hydrogen bonds.