The two-phase flow and transport in an interdigitated air cathode is studied numerically by applying the multiphase, multicomponent transport model previously developed for conventional air cathodes. A computational fluid dynamics (CFD) technique is used to solve the two-dimensional model for the interdigitated air cathode, and the contours of oxygen concentration, water vapor concentration and liquid water saturation as well as the velocity vector fields of gas and liquid phases are obtained. A polarization curve is presented which includes both the single- and two-phase operating regimes. It is found that the threshold critical current density at which the two-phase zone begins to appear inside the porous cathode is higher than that of the conventional air cathode. The maximum liquid water saturation is found to be about 0.045 for a dry inlet at an average current density of 2.07A/cm2. Both gas diffusion and convection play significant roles in oxygen supply and water removal. A higher inlet relative humidity produces a more extensive two-phase zone in the interdigitated air cathode.