Joining of aluminum to copper using Friction Stir Welding (FSW) is a primary manufacturing process that is in most applications followed by a secondary forming process. The objective of this research is to determine the optimum rotational and traverse speeds of Al-Cu Welded by FSW based on the formability of the joint. The formability and strength of Al-Cu joined by FSW are investigated under different operating conditions. Aluminum and copper blanks are welded at three different rotational speeds that are 910, 1280 and 1700 rpm, under three different traverse speeds, which are 16, 29 and 44 mm/min. The base metal used in this study is Aluminum (Al-1050) and copper under two conditions, i.e. as received and annealed. The mechanical properties of base metals and produced joints are evaluated by tensile and hardness tests. The Al-Cu joints by FSW are drawn into flangeless U and cup shapes in order to examine the formability of the joint. The maximum tensile load, punch load and forming index were obtained when Al is welded to annealed Cu at 1700 rpm and 16 mm/min, i.e. highest rotational and lowest traverse speeds, and that is due to the strain hardening of the joint. However, the ductility was maximum at 1280 rpm and 44 mm/min, i.e. moderate rotational and highest traverse speed. It can be concluded that if the Al-Cu joint by FSW will be used further in a forming process, it should be welded at a moderate rotational and high traverse speed in order to avoid strain hardening and improve the ductility of the joint.