Abstract In this study, introduction of tin ions in the SrCoO3−δ oxide is attempted to modify its electrochemical behavior for serving as a cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Doping of tin ions appears to stabilize the cubic Pm-3m phase of the SrCo1−ySnyO3−δ ceramics but generates SrSnO3 precipitates and inhibits the grain growth as y value rises to a level greater than 10%. Obtained at 550°C, the maximum electrical conductivity of SrCo0.95Sn0.05O3−δ reads 545Scm−1. Single cells with a structure of NiO–Sm0.2Ce0.8O2−δ (SDC)/SDC/SrCo0.95Sn0.05O3−δ–SDC are built and characterized. Though SrCo0.95Sn0.05O3−δ is regarded as an MIEC (mixed ionic/electronic conductivity material), adding SDC to SrCo0.95Sn0.05O3−δ guarantees good adhesion to and fine electrical contact with the electrolyte layer, thereby contributing to the reduction in R0 and RP values. The single cell with the SrCo0.95Sn0.05O3−δ–SDC composite cathode at 700°C registers respectively an R0 value of 0.044Ωcm2 and an RP value of 0.109Ωcm2. In the absence of microstructure optimization and hermetic sealing of cells, a high power density of 0.847Wcm−2 is reached. SrCo1−ySnyO3−δ thus emerges to be a promising cathode material for IT-SOFCs applications.