An analysis is presented for mixed convection and heat transfer in a viscous electrically conducting fluid flow at an impermeable stretching vertical sheet with variable thickness. The nonlinear equations that describe the fluid flow, and heat transfer processes have been solved using the Keller-box method. A limited parametric study is undertaken to determine the sensitivity and changes in the flow and temperature fields with respect to variations in the buoyancy parameter, the temperature dependent viscosity and thermal conductivity parameters, the plate velocity power index, and the Prandtl number which are presented in graphical and tabulated formats. To validate the results, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The effects of embedded parameters on the dimensionless velocity profiles and temperature are examined through graphs. The variation of Local Nusselt number is also analysed. One of the important findings of our study is that the velocity distribution at a point near the plate decreases as the wall thickness parameter increases and hence the thickness of the boundary layer becomes thinner when m < 1. Further, the effect of the magnetic field is to reduce the fluid velocity and to increase the temperature field.