A range of 3-azolyl-6-methylimidazo[1,2-b][1,2,4,5]tetrazines was obtained for the first time by electrophilic heterocyclization of 6-allylamino-3-azolyl- and 3-azolyl-6-propargylamino-1,2,4,5-tetrazines in the presence of HgI2. The structures of the starting materials and final products were confirmed by 1Н and 13С NMR spectroscopy, elemental analysis, and X-ray structural analysis.