Sulfonated poly (ether sulfone) (SP-ES) are prepared and optimized considering the transport properties and physicochemical stability. Afterward, nanocomposite membranes composed of SP-ES containing various loading weights of gamma-Fe2O3 nanoparticles are fabricated. Nanoparticles assembled into an aligned form across the membrane by applying magnetic field during solvent casting. The effect of nanoparticles orientation is studied by consideration of the water uptake, membrane ionic conductivity, and activation energy as well as methanol permeability. Aligned membranes have a higher proton conductivity and also lower activation energy for proton migration as well as lower water uptake and methanol permeability. It is also noted that nanocomposite membranes have sufficient thermal stability and high electrochemical performance. Consequently, the anisotropic nanocomposite membranes with oriented nanoparticles demonstrate the ability to have potential application in fuel cells as well as ionic actuators. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.