A new iron aziridination catalyst supported by a macrocyclic tetracarbene ligand has been synthesized., The catalyst, [((TCPh)-T-Me,Et)Fe(NCCH3)(2)](PF6)(2), was synthesized from the tetraimidazolium precursor ((TCPh)-T-Me,Et) (1)(4) and characterized by NMR spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. This iron complex catalyzes the aziridination of electron-donating aryl azides and a wide variety of substituted aliphatic alkenes, including tetrasubstituted ones, in a "C-2 + N-1" addition reaction. Finally, the catalyst can be recovered and reused up to three additional times without significant reduction in yield.