Phosphosilicate gel - SPEEK (Sulfonated Poly Ether Ether Ketone) hybrid nanocomposite membranes are proposed for performance enhancement of polymer electrolyte fuel cell. The nanocomposite membranes are synthesized and characterized at 50 and 60 weight percent of inorganic loading. Phosphosilicate gel particles of varying size (sub micro to nanometer) are synthesized using sol gel approach followed by grinding using planetary ball mill for different time. Transmission Electron Microscopy (TEM) reveals less than 10 nm particle size for 20 hr grinding. Nano composite membrane having inorganic particles of size less than 10 nm exhibits higher values of proton conductivity, ion exchange capacity and water uptake compared to composite membrane comprising of larger (400 nm and above) inorganic particles. The membrane is assembled with the electrode in the unit cell and the polarization characteristics are measured at different operating temperatures. Performance study reveals that between 70 to 8°C the membrane offers best performance in terms of peak power generation and of allowable load current. For the same conditions 40-50 nano-enhancement of peak power generation is achieved by reducing the average gel particle size from sub micro to less than 10 nm. At medium temperature (between 70 to 8°C) the nanocomposite membrane offers more than 100 enhancement of peak power generation compared to that generated by SPEEK membrane. © 2012 Sumy State University.