The effect of iron substitution with nickel cations in La0.65Ca0.35Co0.2Fe0.8−xNixO1−δ oxide on the structural and transport properties of electrode materials for solid oxide fuel cells and electrolyzers was studied in this work. It was shown that Ni3+ cations isomorphically replace Fe3+ /Fe4+ cations in the structure of perovskite. The total conductivity of La0.65Ca0.35Co0.2Fe0.8−xNixO1−δ (x = 0, 0.05) materials was measured in air in the temperature range from 100 to 850°C using the Van der Pauw method.