This paper investigates the effect of chemical reaction and viscous dissipation on MHD mixed convective heat and mass transfer flow of a viscous, incompressible, electrically conducting second grade fluid past a semi-infinite stretching sheet in the presence of thermal diffusion and thermal radiation with Rosseland approximation. The governing boundary layer equations are written into a dimensionless form by similarity transformations. Numerical results for the dimensionless velocity, temperature, concentration profiles as well as for the skin friction coefficient, Nusselt number and Sherwood number are obtained and displayed through graphs and tables for pertinent parameters to show interesting aspects of the solution.