Proton-conducting fuel cells (PCFCs) with a perovskite-type proton-conducting electrolyte show many advantages over conventional oxygen-ion-conducting ceramic fuel cells. Both electrode catalytic activity and electrolyte conductivity determine the performance of PCFCs. Cation non-stoichiometry has a great influence on the catalytic activity and conductivity of perovskite oxides. Here, we propose a PCFC with B-site-cation-deficient perovskites (BCDPs) for all cell components, including cathode, electrolyte, and anode. More specifically, a cell with Ba(Co0.4Fe0.4Zr0.1Y0.1)(0.95)O3-delta (BCFZY-0.95) cathode, Ba(Zr0.1Ce0.7Y0.1Yb0.1)(0.95)O3-delta (BZCYYb-0.95) electrolyte, and Ni-BZCYYb-0.95 anode is fabricated and tested for power generation. Electrochemical impedance spectroscopy in combination with the distribution of relaxation times verify the superior oxygen reduction reaction activity of the BCFZY-0.95 cathode compared to BaCo0.4Fe0.4Zr0.1Y0.1O3-delta and higher proton conductivity of BZCYYb-0.95 than BaZr0.1Ce0.7Y0.1Yb0.1O3-delta. At 650 degrees C, a BCDP cell with a thin-film electrolyte shows a high-power density of 840 mW cm(-2). The cell is stably operated within the test period of 400 h of stability at 550 degrees C.