Cobalt-free double perovskite oxides are promising cathode materials in intermediate-temperature solid oxide fuel cells, and often suffer from low activity in oxygen reduction reactions. Here, we report on Ba deficiency as an effective strategy to enhance the electrochemical performance of cobalt-free double perovskite PrBaFe₂O_5+δ, which is related to the formation and redistribution of oxygen vacancies in double perovskite. The effect of Ba deficiency on crystal structure, surface properties, oxygen content, electrical conductivity, thermal expansion, chemical compatibility with gadolinium-doped ceria (Gd_0.1Ce_0.9O_1.95) electrolyte, microstructure, and electrochemical performance of PrBa_1−xFe₂O_5+δ (x = 0.00–0.03) was evaluated systematically. Our preliminary results suggest that Ba deficiency is a feasible means to tailor the physico- and electrochemical properties of cobalt-free double perovskite, and that PrBa_0.97Fe₂O_5+δ is a potential cathode material for intermediate-temperature solid oxide fuel cells.