The Mg centre in the title compound, [MgBr(2)(C(2)H(7)N)(3)], is penta-coordinated in a trigonal-bipyramidal mode with the two Br atoms in axial positions and the N atoms of the dimethyl-amine ligands in equatorial positions. The Mg(II) centre is located on a crystallographic twofold rotation axis. The crystal structure is stabilized by N-H⋯Br hydrogen bonds. The N atom and H atoms of one dimethylamine ligand are disordered over two equally occupied positions.