In this work, a two-phase, two-dimensional model is developed to investigate the role of interfacial voids at the microporous layer (MPL) and catalyst layer (CL) interface on the polymer electrolyte fuel cell (PEFC) performance. The model incorporates the MPL vertical bar CL interfacial region as a separate domain and simulates two-phase transport within the interfacial voids. Different case studies, including the experimentally-measured MPL vertical bar CL interface and a perfect contact interface, are conducted. Model simulations indicate that the MPL vertical bar CL interfacial morphology has a significant effect on performance, particularly in the high current density region (>1.0 A/cm(2)). The interfacial voids at the MPL vertical bar CL interface are found to retain liquid water during operation and induce mass transport resistance, resulting in nearly a 20% reduction in the limiting current density when compared to perfect interfacial contact. The liquid water saturation retained at the interface and the magnitude of the mass and charge transport resistance induced by the interface are found to be highly dependent upon the geometry and size of the interfacial voids. Finally, simulations indicate that the morphology of the MPL vertical bar CL interface affects the location where reactions tend to occur in the CL, and also has a direct impact on the temperature distribution within the cathode. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.