Ni–BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (Ni–BZCYYb) membrane shows improved and stable performance in dry H 2 and CO 2 (Fang et al., ACS Appl. Mater. Interfaces 6 (2014) 725–730). However, the stream from steam methane reforming contains high contents of H 2 O, CO 2 , and CO, which poses crueler challenges to the chemical stability of Ni–BZCYYb membrane than dry H 2 and CO 2 . In this work, we tested the Ni–BZCYYb membrane in wet H 2 and CO 2 which generated high content of H 2 O and CO due to reverse water gas shift (RWGS) reaction at high temperature. High content of H 2 O improves the proton conductivity of BZCYYb and hydrogen transport through the membrane. On the other hand, H 2 content reduction and decomposition of BZCYYb promoted by high content of H 2 O lead to performance degradation. The steady-state hydrogen flux may increase or decrease depending on the balance among these effects. Besides, CO-induced Ni corrosion was found in both surface and bulk due to metal dusting. In general, Ni–BZCYYb membrane still displayed much better performance stability in wet H 2 and CO 2 than Ni–BaCe 0.8 Y 0.2 O 3−δ and Ni–BaZr 0.1 Ce 0.7 Y 0.2 O 3−δ composites, making it a candidate material system for further studies aimed at membrane processing of hydrocarbons.