The title chiral quaternary ammonium salt, C13H25N4+·I−, was synthesized through the Menschutkin reaction between the cage aminal (2S,7S)-1,8,10,12-tetra­aza­tetra­cyclo­[8.3.1.18,12.02,7]penta­decane and ethyl iodide. The quaternization occurred regioselectively on the nitrogen with major sp3 character. The crystal structure consists of anions and cations separated by normal distances. Ions are not linked through C—H⋯I hydrogen bonds.