MgSO4 and (NH4)(2)SO4 are the main impurities in the hydrometallurgical systems of zinc and manganese. To understand their influences on MgF2(s) solubility, which the fluoride in these systems is expected to remove, we measured MgF2(s) solubility in NH4Cl, (NH4)(2)SO4 and MgSO4 aqueous solutions at 298.15 K. It was found that the MgF2(s) solubility exhibits salt-in effect in the (NH4)(2)SO4(aq) and NH4Cl(aq) solutions, but salt-out and salt-in effects in the MgSO4(aq) solution. Furthermore, the MgF2(s) solubility in (NH4)(2)SO4(aq) is higher than in NH4Cl(aq) solution. Ionic association reactions have been derived to interpret the above solubility phenomena.