A family of proton conducting membranes based on cross-linked poly(vinyl alcohol), PVA, has been synthesized and characterized. The influence of surface-functionalized silica particles on the membrane properties has been evaluated by means of 1H-NMR, vibrational spectroscopy, thermal analysis and electrochemical characterization. The study revealed that the crystallinity of the polymer, the proton diffusivity and the water retention are strongly affected by the presence of the inorganic compound. Conductivity measurements and preliminary fuel cell tests agreed in determining the best PVA/silica ratio among the various compositions explored and demonstrated the potentiality of the selected membranes as electrolytes in fuel cell devices.