The structure of a salt of diprotonated endo-3-aminotropane crystallized with a copper(II) anionic cluster is reported, viz. (C 8 H 18 N 2)[CuCl 3 (NO 3)(H 2 O)]. Neither ion in the salt has been structurally characterized previously. In the crystal, the ions pack together to form a three-dimensional structure held together by a network of intermolecular N - H⋯O, O - H⋯Cl and N - H⋯Cl hydrogen-bonding interactions. Selective crystallization of the title compound can be considered as a simple method for the separation of the exo and endo isomers of 3-aminotropane.