Herein, a probabilistic model for predicting the effect of post-weld treatment on the fatigue performance of the welded joints in tubular truss bridges is described. Specifically, a probabilistic LEFM-based model is first developed for the fatigue analysis of single untreated and treated crack sites in tubular K-joints. A systems reliability approach is then proposed for the analysis of tubular structures with multiple potential crack sites. Using this approach, it is then demonstrated that significant improvements in the fatigue reliability of tubular joints with dimensions common to bridge structures can be obtained with post-weld treatment, even when the influences of the various untreated and treated potential crack sites are considered.