© 2020, The Brazilian Society of Mechanical Sciences and Engineering.This study explores the thermal distribution of high-strength engineering alloys during the friction stir welding process (FSW). Materials which are difficult to weld or are unweldable by conventional welding processes can be successfully welded by FSW. The specific analysis and modification of the process require an understanding of the actual mechanism of the process. Therefore, a transient, three-dimensional, thermo-mechanical finite element model (FEM) for FSW was developed. The model calculates the temperature distribution during the welding process considering various boundary conditions such as rotational speed, linear speed, normal pressure, tool diameter and material properties. The thermo-mechanical FEM calculations consider the effects of conduction and convection heat transfer. The numerical results are successfully compared and validated by experimental results published in the literature for aluminium alloy, titanium alloy and steel (mild and bainitic) as workpiece materials. The model was found to be useful for understanding the effects of changes in different system parameters, and for selecting the optimum welding conditions before undertaking high-cost physical testing.