The crystal structure consists of a strongly hydrogen bonded network of tris(N-ethylammonium)ammonium cations, Cu3Cl126- trimeric species, and Cl- anions. The Cu3Cl126- trimers are formed by two distorted tetrahedral CuCl42- anions linked to a central square planar CuCl42-anion via semicoordinate Cu-(ClCu)-Cu-... mu(1) bridges. The central copper ion shows only small deviations from ideal D-4h symmetry, while the terminal copper ions show a mild distortion from D-2d symmetry with an average trans Cl-Cu-Cl angle of 136.0degrees. The semicoordinate linkages provide a ferromagnetic exchange pathway between the copper ions with J/k = 6.91(3) K. Short (ClCl)-Cl-... contacts (3.67-3.90 Angstrom) lead to very weak antiferromagnetic coupling between the ferromagnetically coupled trimers.