Abstract: Joining Mg to Al is challenging because of the deterioration of mechanical properties caused by the formation of intermetallic compounds (IMCs) at the Mg/Al interface. This study aims to improve the mechanical properties of welded samples by preventing the fracture location at the Mg/Al interface. Friction stir welding was performed to join Mg to Al at different rotational and travel speeds. The microstructure of the welded samples showed the IMCs layers containing Al₁₂Mg₁₇ (γ) and Al₃Mg₂ (β) at the welding zone with a thickness (< 3.5 µm). Mechanical properties were mainly affected by the thickness of the IMCs, which was governed by welding parameters. The highest tensile strength was obtained at 600 r/min and 40 mm/min with a welding efficiency of 80%. The specimens could fracture along the boundary at the thermo-mechanically affected zone in the Mg side of the welded joint.