In this work, an analysis of a joint connected by Friction Stir Spot Welds (FSSW) is performed from both a numerical and an experimental point of view. The focus is to evaluate which structural parameters are strictly relevant to FSSW modeling in FE. Their determination is of great importance for the elaboration of a new numerical model of a joint combining efficiency, accuracy in results and fast calculation. To this purpose, the FSSW joint is analyzed by means of a complex 3D FE model which allows to evaluate, in a parametric manner, the multifaceted internal geometry of the joint and the distribution of material mechanical characteristics after welding. It is possible to evaluate the structural behavior of the joint when new structural characteristics of the joint have been verified after the welding process.