In this work, laser shock peening (or simply laser peening) is investigated for the first time as a post welding treatment for dissimilar foils joined via the fully-mechanical, high-velocity laser impact welding technique. Single and double laser peening shots were applied to laser-impact-welded foils using three different metallic material combinations. Subsequent lap shear testing showed that single-shot laser peening increased the average weld strength by 12% to 25%, depending on the flyer and target material combination. In contrast, with double-shot laser peening, the average weld strength decreased regardless of the flyer and target materials involved. Scanning electron microscope images revealed wavy weld interfaces and increased interlocking between the foils for the single-shot laser peening treatments as compared to the initial “flat” weld interface geometry, thereby leading to greater flyer/target weld strength. In the double-shot laser peening treatments, however, separations and melting were observed along the weld interface due to rebounding and excessive plastic heat dissipation of the foils. The findings of this study reveal the first insights and effects regarding the application of laser shock peening as a post-welding treatment beyond conventional fusion-based welding to high-velocity impact welding methods.