This research presents the mechanical and metallurgical properties of dissimilar joints of AA5083-O and AA6061-T4 aluminum alloy. Two rotational speeds, 630 and 1600 rpm and three traverse speeds 16, 25, and 40 mm/min were applied to perform the joining process. Macrostructural observations were done to evaluate the weld quality and some semi-circular profiles appeared on the trailing side of the weld and flash were also visible on the retreating side of the joint. Optical microscopy was used to determine the orientation and distribution of the grains in the weld and the adjacent zones. Dynamic recrystallization was evident in the dissimilar joint and the fine grain structure confirmed this. The material in the stir zone contained a mixture of both materials but AA6061-T4 which was fixed on the advancing side dominated the stir zone and thus it influenced the joint performance. Mechanical properties of the joints i.e. ultimate strength, elongation, and microhardness were determined for different weld zones and material combinations. Material combinations included joints made of similar AA5083-O or AA6061-T4 as well as dissimilar joints of AA5083-O and AA6061-T4. The dissimilar joint exhibited intermediate mechanical properties. Hardness values were generally less in the advancing side compared to the retreating side and also they increased from the bottom towards the top of the joint.