We examine the combined effects of Soret and Dufour diffusion and porous impedance on laminar magnetohydrodynamic mixed convection heat and mass transfer of an electrically-conducting, Newtonian, Boussinesq fluid from a vertical stretching surface in a Darcian porous medium under uniform transverse magnetic field. By applying two equal and opposing forces along the x-axis, the sheet is stretched with a speed proportional to the distance from the fixed origin x = 0. The steady-state boundary layer equations are non-dimensionalized into non-similar form and then solved numerically by the local non-similarity method with shooting quadrature. The effects of the Darcian linear porous drag parameter (Da), Soret number (Sr), Dufour number (Du), Prandtl number (Pr), Schmidt number (Sc), magnetohydrodynamic parameter (M) and concentration-to-thermal-buoyancy ratio parameter (N), on the fluid velocity, temperature, concentration, local skin friction, Nusselt number function and Sherwood number function distributions in the regime are depicted graphically and analyzed in detail. Applications of the study include magnetic materials processing and chemical engineering systems.