Herein, we describe the syntheses and structural characterization of bis(carbene)- and tris(carbene)-stabilized organomagnesium cations. The reaction of the N-heterocyclic carbene (NHC) stabilized Grignard reagent (iPrNHC)2Mg(Me)(Br) (1) and Na[BArF4] (iPrNHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, ArF = 3,5-bis(trifluoromethyl)phenyl) in chlorobenzene yields exclusively the bis(NHC)-stabilized dication [{(iPrNHC)2Mg}2(μ-Me)2][(BArF4)2] (2). If the reaction is performed in ethereal or nonpolar arene solvents, 2 undergoes Schlenk-type rearrangements to tris(NHC)-stabilized cations [(iPrNHC)3Mg(Me)][BArF4] (3[BArF4]) and [(iPrNHC)3Mg(Br)][BArF4] (4[BArF4]). These monomeric cations 3[A] and 4[A] (A = BArF4, BPh4) can be independently prepared as single pure products in high yields using common hydrocarbon solvents. The electronic influence of tris(carbene) stabilization is further evidenced by an NHC-mediated ionization of magnesium bromide in the absence of abstraction reagents. The reaction between the sterically unencumbered 1,3,4,5-tetramethylimidazol-2-ylidene (MeNHC) ligand and (MeNHC)2MgBr2 (7) resulted in two geometrically unique cations of the type [(MeNHC)3MgBr][Br]: complex 8a bearing a weakly coordinating bromide anion resulting in a trigonal bipyramidal magnesium center, and complex 8b bearing a noncoordinating bromide anion where the magnesium atom resides in a tetrahedral coordination environment. All isolated complexes were characterized by NMR spectroscopy and single-crystal X-ray diffraction, and their bonding was investigated by density functional theory (DFT).