The two aims of this study are first, determining the optimal friction welding process parameters by using the finite element simulation and second, evaluating the mechanical properties of friction welded part for manufacturing large piston rod in marine diesel engine. Friction welding was carried out with optimal process parameter conditions obtained from the simulation results. The base material used in the investigation was AISI 4140 with an outer diameter of 280mm and an inner diameter of 160mm. In the study, the various tests, including microstructure observation, tensile, hardness, and fatigue tests, were conducted to evaluate the mechanical properties for friction welded joint part.