Abstract Cation ordered perovskites have been recognized as advanced cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study focuses on the effects of Sr substitution on crystal characteristics, electrical properties, and electrochemical performance of SmBa1−xSrxCo2O5+δ (x = 0, 0.25, 0.5, 0.75, and 1.0) as an IT-SOFC cathode material. The electrical conductivity improves with increasing Sr content due to the greater amount of electronic holes originated from the increased interstitial oxygen. The area specific resistances (ASRs) of SmBa1−xSrxCo2O5+δ decrease with Sr content up to x = 0.75 and increase abruptly for x = 1. For x = 0.75, the lowest ASR value, 0.138 Ω cm2, and the highest single cell performance, 1.039 W cm−2 at 600 °C, are obtained. These results indicate that SmBa1−xSrxCo2O5+δ is optimized at x = 0.75 in terms of obtaining the best performance for IT-SOFCs.