Various thermo-mechanical treatments including extruding, swaging and equal channel angular pressing (ECAP) were utilized in order to refine the as-cast microstructure and to improve mechanical properties such as the yield stress and the tensile ductility of the as cast AZ80 magnesium alloy. Depending on the thermo-mechanical treatments utilized for refining the microstructure, the changes in the grain size and mechanical properties due to additional heat treatments were quite different.