BaCeO3 exhibits high protonic conductivity, however, it suffers from low chemical stability. In this study, BaCeO3 was doped with erbia (BCE) and BCE was co-doped with ytterbia (Yb-BCE) and scandia (Sc-BCE) with a view to improve the chemical stability. The undoped sample (BaCeO3) disintegrated into BaCO3 and CeO2 on exposure to CO2 while doped (BCE) and co-doped compositions (Yb-BCE and Sc-BCE) remained almost unaffected indicating effectiveness of the dopant Er3+ and the co-dopants (Yb3+, Sc3+) in improving the chemical stability. The Sc-BCE composition showed better stability. Exposure to water atmosphere led to formation of Ba(OH)2 in BCE and Yb-BCE samples while the Sc-BCE sample exhibited much better stability against water vapor as well. A modified solution combustion synthesis was found to be better for phase formation by calcinations at comparatively lower temperatures. The conduction mode was found to be ionic in dry air and mixed protonic–ionic in wet air atmosphere. In wet Argon–Hydrogen mix (AHM), the conduction mode was primarily protonic. The co-doped compositions, Yb-BCE and Sc-BCE showed higher conductivity compared to BCE and Yb-BCE exhibited the best conductivity in wet AHM.