This article presents an approach related to the dissimilar friction stir welding of AA6082 and AA7075. The effects of tool type, tool rotational speed and welding speed on the ultimate tensile strength (UTS) and percentage of elongation were investigated using grey relational analysis and then the optimal combination was determined. The results of a series of analyses revealed that the tool type 4, a tool rotational speed of 1000 rpm/min and a welding speed of 100 mm/min correspond to the optimal condition. Except for tool rotational speed, the other factors are significant at 95% and affect the grey relational grade value with a percentage contribution sorted in descending order as welding speed (48.7%), tool type (27.48%) and tool rotational speed (15.13%). A confirmation experiment was carried out to verify the optimised parameters. The result indicated that an improvement was achieved in ultimate tensile strength and percentage of elongation.