Preloading, or potential overloading early in the fatigue spectrum, may redistribute the local residual stress at the weld due to the stress concentration caused by weld geometry, thereby altering the joint’s fatigue strength. This study investigates the effect of preloading on the fatigue life of non-load-carrying circular flat studs made from S960 steel. Nominal preloading up to the material’s yield strength was applied to induce plastic deformation in the weld transition area. The preloaded specimens were then subjected to constant amplitude fatigue testing, and the results were compared with the fatigue life of specimens without preloading. The results indicate that preloading improves fatigue life, demonstrating a clear relationship between preloading and fatigue strength, which also highlights the benefits of high-strength steel in welded structures subjected to fatigue.