Underwater Friction Stir Welding (UFSW) is an advanced solid state welding technique that allows welding to be efficiently carried out underwater by utilising a non-consumable high rotating tool. The use of UFSW process will simplify the process of joining the two metals underwater. This present study will study the best welding parameters for producing good aluminium AA5083 plate butt joint bu UFSW process. Three experiments were conducted at several selected different welding parameters. It was found that the best joining occurred at 1700 rpm of rotational speed, 16 mm min-1 of travel speed, 50 sec of dwell time and 2° of tilt angle with underwater condition at 100°C water temperature. © 2016 I.M. Ikram et al.