A novel composite membrane for direct methanol fuel cells (DMFCs) have been prepared by incorporation of polystyrene sulfonic acid (PSSA) functionalized multi-walled carbon nanotubes (PSSA-MWCNTs) into sulfonated polyether ether ketone (sPEEK) matrix. The composite membranes were prepared with different weight percent of PSSA-MWCNTs by adopting solution casting procedure. Interaction of PSSA-CNTs with sPEEK was confirmed by different characterization techniques. Uniform dispersion of PSSA-CNTs in sPEEK improves the mechanical and thermal properties along with ionic conductivity in turn decreasing the methanol crossover through the membrane in comparison with pristine sPEEK membrane. Composite membranes of sPEEK-PSSA-CNTs showed higher DMFC performance in relation to pristine sPEEK and Nafion membranes. (C) 2014 Elsevier B.V. All rights reserved.