The paper describes the preparation of hybrid membranes using a trisilanol phenyl polyhedral oligosilsesquioxane (TSP POSS) as filler, ethylene glycol (EG) as cross-linker and sulfonated poly(ether ether ketone) [SPEEK] (DS similar to 65%) as polymer matrix. The performance of membranes has been evaluated in terms of thermal stability [by thermogravimetric analysis (TGA), differential scanning calorimetery (DSC)], water uptake, proton conductivity and X-ray diffraction (XRD) analysis. Morphology of the membranes has been investigated using scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and atomic force microscopy (AFM). The addition of EG has increased the proton conductivity and dimensional stability of SPEEK matrix whereas incorporation of a small amount of TSP POSS to SPEEK/EG membranes has resulted in the decrease in water uptake and proton conductivity of the hybrid membranes. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.