The focus of the work was on layered perovskite-related materials as potential electrolytic components of devices such as proton-conducting solid oxide fuel cells for clean energy. The possibility of isovalent substitution in the In-sublattice of the two-layer perovskite BaLa2In2O7 has been experimentally investigated. It has been found that the replacement of half the structural positions of In3+ ions by Y3+ ions leads to an increase in oxygen ion conductivity due to an increase in their mobility as a result of an increase in interlayer space. It is shown that the increase in proton conductivity upon doping is due to both an increase in the mobility of the protons and an increase in their concentration. The BaLa2InYO7 exhibits predominantly proton conductivity at temperatures below 500 °C.