The MIEC La1.5Sr0.5Ni1-yFeyO4 (y=0.1-0.4) oxides have been studied as cathode materials with La0.88Sr0.12Ga0.82Mg0.18O3-δ (LSGM) electrolyte. Total conductivity, thermal expansion, oxygen nonstoichiometry, and chemical compatibility with LSGM and Ce0.8Sm0.2O1.9 (SDC) were determined. The following fuel cells were tested: La1.5Sr0.5Ni1-yFeyO4 (y=0.1, 0.2, 0.3, 0.4)/SDC/LSGM/Sr2N0.75Mg0.25MoO6 (SNMM) and La1.5Sr0.5Ni0.6Fe0.4O4/SDC/LSGM/SDC/NiO-SDC. For the former, the maximum power densities were 218, 274, 222, and 390 mW/cm2 at 850 °C in case of y equal to 0.1, 0.2, 0.3, and 0.4, respectively. The latter cell showed maximum power density of 341 mW/cm2 at 850°C.