The structure of the title compound, C(12)H(16)N(5) (+)·I(-), shows that the methyl-ation reaction with CH(3)I occurred at the imine N atom at position 5 of the 3,6,7,8a-tetra-hydro-2H-diimidazo[1,2-c:1',2'-e]pyrido[1,2-a][1,3,5]triazine system. In the cation, the sp(3)-hybridized C atom belonging to the fused dihydro-pyrine and dihydro-1,3,5-triazine rings deviates by 0.514 (3) Å from the best plane defined by the remaining cationic non-H atoms. The fused dihydro-pyridine and dihydro-1,3,5-triazine rings are each in a half-chair conformation with the sp(3)-hybridized C atom as a flap. The iodide anion is 3.573 (2) Å from the methyl-ated N atom and exhibits five short C-H⋯I(-) contacts with distances less than 3.16 Å. The structure has been determined from a non-merohedral twin with twin law [-1 0 0 0 - 1 0 0.115 0 1], minor domain = 0.1559 (12).