The title compound, [Cu2(CN)3(C6H18N4)] or [Cu(trien)(CN)Cu(CN)2], where trien is triethyl-ene-tetra-mine, is a mixed-valence complex crystallizing as discrete mol-ecules, with Cu(I) and Cu(II) ions linked by a bridging cyanide group. The Cu(II) ion is in a square-pyramidal coordination environment, with the N atoms of the tetra-dentate trien ligand occupying the basal positions and Cu-N bond lengths in the range 2.028 (4)-2.047 (4) Å. An N-bonded cyanide group is in the apical position, with a slightly longer Cu-N bond length of 2.127 (4) Å. The Cu(I) ion exhibits a trigonal-planar coordination geometry, bonded to the C atoms of the bridging cyanide group and two terminal cyanide groups with Cu-C bond lengths in the range 1.925 (4)-1.948 (5) Å. In the crystal, hydrogen bonding involving the tertiary N-H groups of the trien ligand and N atoms of symmetry-related terminal cyanide groups links mol-ecules into a ribbon extending in the b-axis direction.