Various designated precipitation hardening and cold working have been employed to improve mechanical properties of aluminum–magnesium–silicon alloys. The aim of this study is to study how both high strength and excellent ductility could be achieved. Two main processes are competing to each other when the cold working is combined with precipitation hardening. They are dislocation annihilation during age treatment which improves ductility; and dislocation pinning by precipitates which increases strength of materials. In this paper, the mechanical properties of cold rolled AA6061 sheets in pre-aging, single and double aging conditions were compared. The different sequences of precipitation hardening and cold working were employed to achieve both high strength and excellent ductility. The results show that the amount of initial cold rolling and pre-aging may have negligible effect on the strength and hardness but significant effect on the ductility of alloy.