The present work describes the effect of fluorine and chlorine doping on the chemical stability of proton conductors Ba₂In₂O₅, Ba₄In₂Zr₂O₁₁, and Ba₄Ca₂Nb₂O₁₁ against carbon dioxide and water steam. It was proved that both undoped and halide-doped compositions demonstrate good chemical stability under H₂O treatment without degradation and without any hydrolytic decomposition. The hydration process leads to the change in the crystal structure only. The treatment in the CO₂/air (1:1) atmosphere (500 °C, 10 h) leads to the decomposition of undoped samples only. Halide-doped samples retain their structure without detectable products, that is, they are more chemically stable compared with undoped compositions. The method of halide doping can be used as the promising technique for obtaining the new perovskite-related materials with high level of chemical stability.