In this study, the fatigue behaviour of spot friction welded joints of Al 5083-O was investigated using experimental and numerical approaches. In the experimental part, a single cover butt joint of aluminium sheets with a thickness of 2 mm was fatigue tested under constant amplitude cyclic loadings. The sheets were connected using a spot friction welding technique with constant welding parameters of tool rotational speed, holding time, travelling speed, and shoulder plunge depth. Fatigue cracks were initiated in the vicinity of the weld notch and then propagated along the circumference of the weld's nugget. In the numerical part, a three-dimensional finite element model was developed to determine stress and strain distributions in the spot friction welded joint and to predict the fatigue life using three approaches of Morrow, modified Morrow, and Smith-Watson-Topper. The results showed a good agreement between the fatigue life predictions and experimental data.