The use of thermoplastics in various fields like aerospace, automotive, medical and packaging industries is growing day by day, due to their light weight and compactness. In some instances, the plastic components are required to be welded. In this research study, process parameters used for the ultrasonic welding of thermoplastics which produces highest weld strength for complex use in the above said applications is carried out. Also, the possibilities of welding dissimilar plastics are also tested. Tensile testing of above welded samples fabricated through injection moulding was carried out for all possible welds and the ultimate tensile strength was calculated in each case. Of all the welded specimens, at given parameters like weld time, weld pressure and energy director, it is observed that ultimate tensile strength of ABS (8.89 N/mm2) is highest. The test results shows that this technique to weld thermoplastics can be used in various automobile, aerospace, electrical, medical, packaging industries. © 2018 SAE International. All Rights Reserved.