Protonic ceramic membrane fuel cells (PCMFCs) based on proton-conducting electrolytes have attracted much attention because of many advantages, such as low activation energy and high energy efficiency. A stable, easily sintered perovskite oxide BaCe0.5Zr0.3Y0.16Zn0.04O3−δ (BCZYZ) as electrolyte for proton-conducting solid oxide fuel cells (SOFCs) with Sm0.5Sr0.5CoO3−δ (SSC) composite cathode is investigated. By fabricating thin membrane BCZYZ electrolyte (20 μm) synthesized by a modified Pechini method on NiO–BCZYZ anode support, PCMFCs are assembled and tested by selecting SSC perovskite cathode with high mixed ionic and electronic conductivities. An open-circuit potential of 1.015 V, a maximal power density of 528 mW cm−2, and a low polarization resistance of the electrodes of 0.15 Ω cm2 is achieved at 700 °C. The results indicate that BCZYZ proton-conducting electrolyte with SSC cathode is a promising material system for SOFCs.