A method for preparing sulfonated poly(ether ether ketone) (SPK)-zeolite-zirconium hydrogen phosphate (ZrP) nanocomposite PEM by in situ infiltration and precipitation has been reported. First time we are reporting the infiltration of zeolites in the pores/cavities created by water-soluble surfactant in the polymer electrolyte, for accommodating proton conductor (ZrP). Infiltration of zeolite and surface modification with ZrP of SPK membrane improves the thermal, mechanical strength, oxidative and dimensional stabilities along with water retention capacity, which are the essential requirement for PEMs. These nanocomposite membranes showed slightly lower proton conductivity (2.91-3.35 x 10(-2) S cm(-1)), in comparison to Nafion117 (N117) membrane at 30 degrees C. But at 70 degrees C, their selectivity parameter was increased by three times in comparison to N117, due to their equal conductivity and extremely low methanol permeability. This indicates suitability of these PEMs for fuel cell applications at moderate temperature. (c) 2008 Elsevier B.V. All rights reserved.