The analysis of tensile fracture pattern in correlation with the welding parameters and metallurgical test results enlighten in service weld quality of material being welded. Modern industry is seeking to establish optimum method which can incorporate multiple properties within single structural component; welding is one of the way to do so. Hence, dissimilar material welding is exploited in recent years. Friction stir welding (FSW) is a solid state, hot-shear process. It can eliminate or reduce detrimental problems associated with melting (in fusion welding processes) of materials such as porosity, solidification cracking, and residual stress. These issues may trigger premature failure of the joint. Cu with SS welded joints are suitable enough to construct first wall and divertor; structural components of international thermo-nuclear experimental reactor. This is the reason of present study focuses on to friction stir welding of Cu with SS aiming to improve mechanical properties. It can be achieved by optimal combination of welding parameters. Dissimilar metal joining through friction stir welding process has been adequately evaluated in recent past. However, limited research work has been reported in present system. Hence, a fully experimental approach has been adopted in the present investigation to exploit the effect of assisted source on to joint formation. A gas tungsten arc welding torch in the range of 20A to 60A with an interval of 20A is applied at the leading side of the friction stir welding tool on joint line as assisted heating source. Furthermore, 15 psi as well as 30 psi of compressed air and 75 ml/min of water cooling is applied at the trailing edge of joint as assisted cooling while transverse phase of process. In conjunction with theses welding parameters, authors are aiming to investigate tensile fracture mechanism on the scale of micro-hardness and metallurgical test results. Tensile test result is reported that the joint efficiency vary from 58% to 72% when material welded with assisted heating whereas 75% in the case of normal mode of friction stir welding. However, there was a steep drop in the joint efficiency when forced air/ water cooling of joint was employed during the process. The joint efficiency was only 29% with water cooling whereas slight improvement observed (43%) when material welded with compressed air cooling. Maximum hardness in the weld nugget is obtained for conventional FSW samples. Most of the samples tested for mechanical strength fractured in the nugget area. Some of them fractured from the interface of Cu/SS or suspended SS particles (present at weld nugget) Reported poor strength. Most of the welded samples wear fractured from Cu/SS interface during additional cooling while friction stir welding. Higher tensile strength and ductile fracture behavior are observed in joints fabricated with additional heating as compared to additional cooling. This indicates improved dynamic deformation resulting due to better material flow within the joint for heating assisted FSW joints as compared to force cooled joints