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The cobalt-free layered perovskite oxides Sm1−xLaxBaFe2O5+δ (x = 0–0.5) (SLBFx, for short) have been systematically investigated to evaluate the feasibility of using them as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). SLBFx powders with an orthorhombic structure were synthesized by the EDTA–glycine combustion method and were observed to be compatible with LSGM and SDC electrolytes below 1250 °C. The electrical conductivities of the SLBFx samples significantly increased with the substitution of La for Sm, with the highest conductivity of 37.8 S cm−1 obtained for the SLBF0.5 sample at 600 °C. Of the La-doped SmBaFe2O5+δ series samples, SLBF0.2 displayed the lowest thermal expansion coefficient (TEC) and the minimum electrode polarization resistance, with values of 16.51 × 10−6 K−1 in the 50–800 °C range and 0.24 Ω cm2 at 750 °C, respectively. The anode-supported single cell with SLBF0.2 as the cathode was able to generate a maximum power density of 558 mW cm−2 at 800 °C in humidified H2. All things considered, SLBFx materials are good candidates for cobalt-free cathodes in IT-SOFCs.