In this study, DP 800, Usibor 1500 and Ductibor 500P three different high strength steel sheet materials with different thicknesses were joined with electrical resistance spot welding. Welding process is carried out in different material combinations under constant parameters such as electric current, pressure and duration. Tensile specimens for the same and different material pairs welded by resistance spot welding in the form of overlay were prepared according to the standards. Mechanical properties of the welded specimens were evaluated by hardness and tensile-shear tests. The results show that Ductibor 500P material has the highest strength and hardness values. Furthermore, when different types of steels are welded together, the maximum tensile-shear force and elongation achieved are higher than those of the same type of materials.