Active development of electrochemical devices such as proton-conducting fuel cells and electrolyzers should ensure sustainable environmental development. An electrolyte material of a hydrogen-powered electrochemical device must satisfy a number of requirements, including high proton conductivity. Layered perovskites are a promising class of proton-conducting electrolytes. The cationic co-doping method has been successfully applied to well-known proton conductors with the classical perovskite structure ABO3. However, the data on the application of this method to layered perovskites are limited. In this work, the bilayer perovskites BaLa1.9Sr0.1In1.95M0.05O6.925 (M = Mg2+, Ca2+) were obtained and investigated for the first time. Cationic co-doping increases oxygen-ion and proton conductivity values.