The aim of this work is to study the responses to post weld artificial aging (PWAA) of friction stir welds of aluminum alloy 6061-T6 welded at low traverse speed of 125 mm/min and at high traverse speed of 710 mm/min. During welding of either the low traverse speed or high traverse speed weld, the transverse profile of peak temperatures and the local thermal cycles at various distances from the weld center were measured. The transverse hardness profile of the low traverse speed and high traverse speed weld were measured one day after welding and after PWAA. Both immediately after welding and after PWAA the transverse profiles of tensile properties, and strain hardening parameters were determined. Special attention was given to the local properties within the weld weakest region, which greatly affect the overall strength and ductility of the welded joints. The results show that PWAA greatly improve the tensile properties of the high traverse speed weld. For the low traverse speed weld, while PWAA slightly improves yield and ultimate tensile strength, it deteriorates the uniform elongation due to the severe mismatch in local mechanical properties between the various zones of the weld.