Recently, fabricating low-cost and high-performance proton exchange membranes (PEMs) with carbon nanotubes (CNTs) and chitosan (CS) have been extensively studied. Herein, we reported a facile but effective method to prepare CS-based PEM with polydopamine (PDA) functionalized CNTs (PDA@CNTs). The CS/PDA@CNTs composite membranes were prepared by incorporating PDA@CNTs into CS matrix followed by ion cross-linking with sulfuric acid. Due to the hydrogen bonding between the CS matrix and PDA coating, the thermal, mechanical and oxidation stability of the CS/PDA@CNTs composite membranes were improved. Moreover, the proton conductivity was also improved owing to the improved dispersion of PDA@CNTs in the CS matrix and the electrostatic interaction between PDA@CNTs and CS matrix. The maximum proton conductivity can reach to as high as 0.028 S cm(-1) under 80 degrees C with 2 wt% loading of PDA@CNTs. These results indicate that the CS/PDA@CNTs composite membranes have great potential to be used as PEMs in fuel cells. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.