The title compound, C(18)H(28)N(5)O(2) (+)·I(-), was observed as a main product in an intended 1:1 reaction between 4-iodo-nitro-benzene and 1,4-diaza-bicyclo-[2.2.2]octane (DABCO). In the reaction, DABCO undergoes a ring opening to yield a quaternary salt of DABCO and 1-ethyl-4-(4-nitro-phen-yl)piperazine with an iodide anion. The crystal structure determination was carried out as no crystal structure had been previously reported in the investigations describing the corresponding reaction with 4-chloro-nitro-benze. Indeed, the crystal structure of the title compound confirms the mol-ecular composition proposed earlier for the analogous chloride salt. The cation conformation is similar to the previously reported dinitro analogue 1-{2-[4-(2,4-dinitro-phen-yl)piperazin-1-yl]eth-yl}-4-aza-1-azoniabicyclo-[2.2.2]octane chloride [Clegg et al. (2004 ▶). Acta Cryst. E60, o291-o293]. The crystal packing is dominated by cation⋯I(-) inter-actions in addition to weak inter-molecular C-H⋯O(2)N and C-H⋯N inter-actions between the cations.