The oxygen (O-2) transport resistance at the gas diffusion layer (GDL)-air channel interface in a proton exchange membrane fuel cell (PEMFC) is numerically investigated. The interfacial O-2 resistance under the two-phase flow conditions is needed in modeling fuel cell performance. This work focuses on simulating the effect of water droplets on the GDL surface on the mass transfer resistance at the interface. Multiple droplets are placed at the center of channel width and spaced uniformly in the flow direction. The variation of interfacial O-2 transport resistance is characterized with the non-dimensional Sherwood number (Sh). The numerical technique is validated by comparing the fully developed Sh (in the absence of droplets) to the established values in the literature. Parametric simulations are performed for variable air Peclet number (varied due to changing superficial air velocity), non-dimensional droplet size and uniform spacing. Correlations are developed to express the Sh variation in terms of the aforementioned variables and the location in the channel. The maximum error of the correlations among numerically generated 999 data points is 11%. (C) 2014 Elsevier Ltd. All rights reserved.