Nickel-substituted double-perovskites, LnBaCo1.6Ni0.4O5+δ (LnBCN, Ln=Pr, Nd and Sm), are investigated as potential cathode materials for intermediate-temperature solid-oxide fuel cells based on the Ce0.8Sm0.2O1.9 (SDC) electrolyte. The LnBCN materials exhibit high chemical compatibility with the SDC electrolyte at 950°C for 2h. Substitution of Ni for Co decreases the thermal expansion coefficient and the electrical conductivity, as compared with the nickel-free samples while retaining desirable electrochemical performance. The area-specific resistances of the LnBCN samples on the SDC electrolyte where Ln=Pr, Nd, and Sm at 700°C are 0.056, 0.077, and 0.11Ωcm2, respectively. For Ln=Pr, Nd, and Sm cathodes, the maximum power densities of the electrolyte-supported Ni-SDC/SDC/LnBCN single cells with a 0.3 mm thick SDC electrolyte reach 732, 714, and 572mWcm−2 at 800°C, respectively. These results show that nickel-substituted LnBCN double-perovskites are potential cathode candidates for use in IT-SOFCs.