Magnesium alloys, due to their attractive characteristics, are being utilized as lightweight structural materials in aerospace, automotive, and various other industries. Further design flexibility can be obtained by joining the Mg alloys to other materials with outstanding performance, such as aluminum alloys. In this study, Al-6062 and Magnesium AZ31B have been joined through friction stir welding (FSW) using the high-speed steel (HSS) tool. The impact of two important process parameters, including spindle speed and welding speed, has been evaluated on ultimate tensile strength (UTS). In addition, the effect of the advancing side has also been assessed. Analysis of variance has been performed based on full factorial design. For maximum UTS, the study suggests spindle speed and welding speed of 100 rpm and 50 mm/min respectively with magnesium on the advancing side. The weld strength is 110% higher than that of magnesium-magnesium weld joint.