In the title hydrated mol-ecular salt, [Mg(H(2)O)(6)](C(13)H(9)BrNO(4)S)(2)·2H(2)O, the Mg(2+) ion (site symmetry ) adopts a near regular MgO(6) octa-hedral coordination geometry. In the anion, the dihedral angle between the aromatic rings is 2.5 (2)° and an intra-molecular O-H⋯N hydrogen bond generates an S(6) ring. In the crystal, the components are linked by O-H⋯O and O-H⋯Br hydrogen bonds.