Kinetic and mass-transport properties were investigated for the oxygen reduction reaction for Nafion® 117 and sulfonated poly(arylene ether sulfone) membranes, both pre- and post-sulfonated analogs (SPES-40 & SPES-PS) under 100% relative humidity and as a function of pressure (1–4 atm total pressure, 323 K) and temperature (303–353 K, 3 atm) using a solid-state electrochemical cell. Kinetic parameters were obtained using slow-sweep voltammetry while mass-transport parameters, the diffusion coefficient (D) and solubility (C), were obtained using chronoamperometry at a Pt (microelectrode)|proton exchange membrane (PEM) interface. The oxygen reduction kinetics were found to be similar for all the membranes at the Pt microelectrode interface. The temperature dependence of O2 permeation parameters showed identical trends for the membranes studied while the pressure dependence of O2 permeation parameters displayed some differences. Despite higher ion exchange capacities and hence higher water uptake, the two SPES membranes exhibited relatively lower values of D as compared to Nafion® 117. The results are discussed in the context of their different microstructures.