A numerical study is performed to analyze the effect of mass transfer on unsteady MHD free convection flow of dissipative fluid past an infinite vertical porous isothermal plate taking into account viscous dissipative heat under the influence of transverse magnetic field. The governing equations are solved numerically by applying finite difference method. The velocity, the temperature and the concentration are studied for different parameters like magnetic field parameter M, suction parameter g, Schmidt number Sc, Eckert number E, Grashof number Gr and modified Grashof number Gm. The numerical results are presented graphically for different parameters. The numerical values of Skin-frictions are presented in tabular form.