This paper presents the time-variant structural performance evaluation of the Certosa cable-stayed bridge built in Milan, Italy. Since the pylons showed some traces of damage, a rehabilitation intervention has been carried out after fifteen years of lifetime. In order to investigate the effectiveness of the rehabilitation intervention, a novel procedure for the durability analysis of concrete structures subjected to diffusive attacks from external aggressive agents is applied. Based on this procedure, both the deterministic and probabilistic time-variant structural performances are analyzed with respect to proper indicators considering two separate cases: without and with rehabilitation intervention. The direct comparison of the results demonstrates that the adopted intervention enhances the structural performance over time and reduces its dispersion effects.