The title compound C14H29N4+·I− salt, was obtained by the reaction of cage adamanzane-type aminal 1,3,6,8-tetra­aza­tricyclo­[4.3.1.13,8]undecane with heptyl iodide. In the cation, the bond lengths and angles are within normal ranges, except for one N—C(ring) bond distance of 1.542 (3) Å, which is unexpectedly long compared with related compounds. In the crystal, ions are linked through C—H⋯I hydrogen bonds. The crystal studied was a non-merohedral twin with a minor twin domain of 6.56 (5)%.