AbstractThis paper considers the effects of the actual weld profile on the fatigue behavior of welded joints by means of the implicit gradient approach. Different types of geometrical approximation are considered in the analysis. In order to define the fatigue strength reduction factor of the actual weld profile, FE analyses have been considered based on a three‐dimensional scan of the welded joints. Furthermore, the fatigue behavior of butt‐welded joints with a discontinuous undercut is considered, and a comparison has been made with experimental data taken from the literature.