In this research, the dissimilar welding of S500MC to SPFC390 steels by Resistance Spot Welding (RSW) method has been investigated. By performing various mechanical tests, optimum welding parameters (welding time and welding current) were determined. The microstructure of welds were investigated using optical and electron microscope Tensile-shear test has been used to investigate mechanical properties such as fracture energy and fracture strength (maximum shear strength). Also, the hardness profiles were obtained using a microhardness measurement. The welding current was selected between 5 to 14KA and the welding time was set from 6 to 15 time cycles (each cycle is equal to 0.2 seconds). The microstructure study showed that a needle-shaped martensite structure with coarse and rough packages were formed in the welds due to needle-shaped martensite structure with coarse and rough packages associated with RSW. The hardness of the weld center was around 420 HVN, which confirms the martensitic nature of the weld structure.
