AbstractDifferent composite materials made of mixed protonic/electronic conductors, SrCe0.9Yb0.1O3–δ (10YbSC) or BaCe0.9Yb0.1O3–δ (10YbBC), and a mixed oxygen‐ion/electronic conductor, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), were investigated for cathode application in intermediate temperature solid oxide fuel cells (IT‐SOFCs) using a high temperature proton conducting BaCe0.8Y0.2O3–δ electrolyte. Only the LSCF/10YbBC composite was found to be chemically stable. Area specific resistance (ASR) measurements were performed in wet air for LSCF/10YbBC cathodes, changing the weight ratio between the phases and the sintering procedure. The best performance was obtained for the composite cathode containing 50 wt.‐% of LSCF and 50 wt.‐% of 10YbBC, sintered at 1,100 °C. Electrochemical impedance spectroscopy (EIS) measurements of the tested cathodes showed two depressed semicircles in the middle and low frequency range, respectively. Performing ASR measurements at different p allowed us to attribute the two semicircles to charge transfer and oxygen diffusion processes, respectively. The microstructure of the LSCF/10YbBC(1:1) composite cathode was optimised changing the ratio of the particle sizes between the two phases. The lowest ASR values (0.14 Ω cm2 at 700 °C) were observed for the LSCF/10YbBC(1:1) composite cathode with different particle size (sub‐micrometer particles for LSCF and nanometer particles for 10YbBC). Fuel cell polarisation curves demonstrated superior performance of the LSCF/10YbBC (1:1) cathode with respect to Pt.