The structure of the title salt, {[Cu(CN)(C₄H₁₃N₃)]ClO₄}(n), is composed of copper-containing cations and perchlor-ate anions. The Cu(II) atom shows a square-pyramidal coordination, with equatorial positions occupied by the cyanide C atom [Cu-C = 1.990 (3) Å] and the N atoms of the diethyl-enetriamine ligand (average Cu-N = 2.033 Å), while the axial position is occupied by the N atom of a c-glide-related cyanide group. The axial Cu-N distance of 2.340 (3) Å is longer than the equatorial distances, reflecting Jahn-Teller distortion. The Cu(II) cations are linked by the cyanide groups into infinite chains along the c-axis direction. The refinement included a three-component disordered model for the perchlorate ion. Each minor site is stabilized by hydrogen bonds to N-H donors from four surrounding cations, while one O atom of the major perchlorate site forms hydrogen bonds to three of these cations.