In this paper we report elastic modulus and ionic conductivity measurements in proton-exchange membranes based on poly (vinyl alcohol) (PVA), as a function of the acid (H3PO2) concentration and temperature. Tensile stress-strain test (nominal stress) was performed at low rate deformation, with acid concentration between 0.0 to 3.0 given in P/OH ratios. Results show that the elastic modulus, the elastoplastic modulus and the yield stress decrease as acid concentration increases. Ionic conductivity was obtained using the impedance spectroscopy technique on samples with the same acid concentrations, which shows an improvement in ionic conductivity of PVA+H3PO2+H2O within the range 10 i3 - 10 i1 S cm i1 as the acid concentration increases. The results obtained by comparing mechanical and electric properties, show that they are both directly linked to the acid content and water activity, thus these properties can be engineered to meet the appropriate conditions for an efficient fuel cell operation.