In this study, plastic flow joining using a shot peening process was investigated. The substrate used undergoes a large plastic deformation near its surface due to a hit with many shots. Therefore, plastic flow characterized by a shear droop occurs at the edge of the substrate due to shot peening. If an implant made of a dissimilar material is set in a hollow space on the surface of the substrate without any clearance and then shot-peened, it can be joined to the substrate due to the peening droop generated by the large plastic deformation during shot peening. In this method, the availability of the plastic flow, i.e., the peening droop makes the joining of the implant possible. In the experiment, a compressed-air-type shot peening machine was employed. To examine experimentally the influence of working temperature on bondability, equipment with a heating furnace was produced. The influence of processing conditions on the joining of the implant and the substrate was examined. The bond strength increased with the kinetic energy of shots and processing temperature. The improved implant with a step was effective in improving in the bondability. The dissimilar material was also successfully joined to a thin sheet by using of the interaction of peening droops. It was found that the present method using the peening droop was effective for joining dissimilar materials.