Accurate determination of interfacial polarization resistance is essential to characterization of solid-state electrochemical systems based on thin-film electrolytes or membranes. In this study, three methods have been used to determine the interfacial resistance of a composite membrane consisting of 40 vol.% Ni and 60 vol.% BaYxCe1-xO3. The interfacial resistances determined from the dependence of hydrogen permeation rate on membrane thickness were similar to those obtained from a combination of gas permeation with impedance spectroscopy (IS), implying that both approaches are applicable to the composite membrane. Results also indicate that the interfacial resistances are much greater than the bulk resistances under the conditions studied. Further improvement of the hydrogen permeation rate thus depends on reducing the interfacial polarization resistance.