The effect of Minimum Quantity Lubrication (MQL) on performance of Friction Stir Welding (FSW) process for Aluminum Alloy 6061-T651 plates was investigated. MQL was used as a cooling and lubrication medium. Five different levels of rotational speed and three feed speed ranges with and without MQL were tested. The effect of MQL on the mechanical properties of the weld joints was studied throughout means of Ultimate Tensile Strength (UTS) tests. Statistical analyses were run to study the relationship between certain process parameters and response. The results showed that the average UTS of the welds is improved when MQL was applied to most of the process variables. The highest UTS was achieved at spindle speed with 1600 rpm and with feed rate 180 mm/min due to improvement of the grain growth.