Highlights Synthesis of high-entropy perovskite oxide for air electrode in reversible proton ceramic electrochemical cells. Triple-conducting high-entropy air electrodes exhibit excellent structural stability and oxygen catalytic activity. The peak power density and current density of the cell with high-entropy air electrode in the fuel cell and electrolysis modes are 1.21 W cm −2 and − 1.95 A cm −2 at 600 °C, respectively. Reversible proton ceramic electrochemical cell (R-PCEC) is regarded as the most promising energy conversion device, which can realize efficient mutual conversion of electrical and chemical energy and to solve the problem of large-scale energy storage. However, the development of robust electrodes with high catalytic activity is the main bottleneck for the commercialization of R-PCECs. Here, a novel type of high-entropy perovskite oxide consisting of six equimolar metals in the A-site, Pr 1/6 La 1/6 Nd 1/6 Ba 1/6 Sr 1/6 Ca 1/6 CoO 3− δ (PLNBSCC), is reported as a high-performance bifunctional air electrode for R-PCEC. By harnessing the unique functionalities of multiple elements, high-entropy perovskite oxide can be anticipated to accelerate reaction rates in both fuel cell and electrolysis modes. Especially, an R-PCEC utilizing the PLNBSCC air electrode achieves exceptional electrochemical performances, demonstrating a peak power density of 1.21 W cm −2 for the fuel cell, while simultaneously obtaining an astonishing current density of − 1.95 A cm −2 at an electrolysis voltage of 1.3 V and a temperature of 600 °C. The significantly enhanced electrochemical performance and durability of the PLNBSCC air electrode is attributed mainly to the high electrons/ions conductivity, fast hydration reactivity and high configurational entropy. This research explores to a new avenue to develop optimally active and stable air electrodes for R-PCECs.