Membrane additives are used in polymer electrolyte membrane fuel cells (PEMFC) to improve membrane durability due to their effectiveness in scavenging hydroxyl and hydroperoxy radicals. Even though their implication on performance is well-known, their impacts on the durability of other components and failure mechanisms have not been reported. In this study, accelerated stress tests (AST) were used to induce catalyst degradation. The effects of Mn- and Ce-based membrane additives on catalyst degradation were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and neutron activation analysis (NAA). Pt dissolution, Pt agglomeration, carbon surface oxidation, and carbon corrosion were found to be unaffected by the membrane additives. However, the performance impact of these additives became exacerbated with degradation. The effect on Ru crossover was more complex. Ru crossover was lessened in the presence of additives but the performance impact was amplified for a given crossover level. The impact on cathode and anode degradation was deduced to be the combined effect of reduced cathode protonic conductivity and longer proton transport path as the reaction distribution shifted deeper into the catalyst layer. This research highlighted the importance of interaction consideration in component development. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.056301jes] All rights reserved.