This research was conducted to provide information on the results of friction stir welding double sided aluminum 1xxx and aluminum 5xxx. Double-sided FSW is used because research using double-sided FSW is rarely done and there was defects in single-sided and double-sided studies with similar material that have been done. While aluminum 1xxx and aluminum 5xxx were chosen because these materials are rarely used in double sided friction stir welding. The purpose of this study was to determine the effect of tool rotational speed on physical and mechanical properties of double sided aluminum 1xxx and Aluminum 5xxx FSW. The material used in this study is aluminum 1xxx and aluminum 5xxx which have dimensions of 100 mm × 65 mm and have a thickness of 5 mm. Feed rate used is 56,7 mm/minute, while the pin tool rotational speed used is 910 rpm, 1500 rpm and 2280 rpm. The results of the joint were tested by looking at their macro and micro structure, vickers-micro hardness, and tensile test with ASTM E-8 standard. The results show that the lower rotational speed will result in more and more possibilities of defects. At a rotating speed of 910 rpm an incomplete fusion defect occurs. In microstructure, the higher the rotation speed, the smoother the results. For hardness results, the lower the rotational speed, the higher the value. On the results of the tensile strength the highest yield is a rotation speed of 1500 rpm, whis is 96,28 MPa. Whereas for cracking welding faults occurs at a rotating speed of 910 rpm, and at rotating speeds of 1500 and 2280 rpm a ductile fracture occurs.