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The effects of Ca on the properties of PrBa1-xCaxCo2O5+δ (x = 0.0, 0.3, and 0.5) as a cathode material for intermediate temperature solid oxide fuel cells were studied. Higher Ca content in PrBa1-xCaxCo2O5+δ led to a gradual change in phase symmetry from A-site cation ordered double perovskite (x = 0.0) to mixed A-site cation ordered-disordered perovskite (x = 0.3) to A-site cation disordered simple perovskite (x = 0.5). It also led to a decreased oxygen content. Comparing the electrochemical performance of the samples with x = 0.0 and x = 0.5, PrBa0.7Ca0.3Co2O5+δ exhibited the best catalytic activity for the oxygen reduction reaction and maximum power density. This was ascribed to the synergistic effect of the A-site cation ordered-disordered structure, which combined the advantages of a fast oxygen diffusion rate and a relatively short oxygen diffusion distance from the oxygen reduction site to the cathode/electrolyte interface. The maximum power density, which was as high as 2.16 W cm-2, was achieved for the PrBa0.7Ca0.3Co2O5+δ-based single cell with a commercial anode-supported half cell at 800°C. PrBa0.7Ca0.3Co2O5+δ was shown to be a potential cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]