Friction stir welding (FSW) is used to join different lightweight materials, especially aluminium alloys. Dissimilar joints of aluminium alloys have an issue to be weld using the conventional fusion welding. In the present work, two types of dissimilar joints of aluminium alloys were welded as dissimilar butt joints using the FSW method. 5mm thick base metals, consist of AA1100, AA5083 and AA6061, were butt welded to dissimilar joints of AA6061-AA1100 and AA6061-AA5083. Similar welding parameter was used for both of the joints, in which 100 mm/min and 1000 rpm for transverse and rotation speed, respectively. Joints were successful with defect-free internally and externally. However, different flow patterns were observed in the stirred zone due to the different materials flow during the FSW process. The ultimate tensile strength of AA6061-AA1100 and AA6061-AA5083 are 93MPA and 113MPa. Thereby, the joint efficiency of AA6061-AA1100 and AA6061-AA5083 were 80% and 97% compared to AA6061 base metal, respectively.