In the shot peening process, the substrate undergoes large plastic deformation near the surface due to the hit with many shots. A large plastic deformation characterized by a shear droop occurs at the edge of the substrate. When the dissimilar sheets with the edge of the notch geometry are connected without level difference and then the contact area are shot-peened, the sheets can be joined due to the plastic flow generated by a large plastic deformation during shot peening. This method is similar to joining by caulking. The aim of this paper is to investigate the butt joining of high strength steel and dissimilar metal sheets using a shot peening process. The shot velocity and the coverage were controlled in the experiment. The shots used were made of high carbon cast steel and cemented carbide with an average diameter of 0.1 mm. The sheets were high strength steel and aluminum alloys. The influences of processing conditions on the joinability were mainly examined. The joint strength increased with the kinetic energy of shots. Tensile test was also examined to evaluate bond strength. It was found that the present method can be used to enhance the butt joining of high strength steel and dissimilar metal sheets.