Solid polymer electrolytes based on poly (vinyl alcohol) (PVA) complexed with ammonium sulfate (NH4)2SO4 at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by X-ray diffraction (XRD) studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with the increase of ammonium sulfate added up to 5 wt %, after which the degree of crystallinity increases. The complexation of the salt with the polymer was confirmed by Fourier transform infrared (FTIR) spectroscopy. Electrical conductivity was measured in the temperature range of 303–373 K. The conductivity was found to obey Arrhenius formula. The dielectric permittivity e0 was studied as function of temperature and frequency, respectively. The data showed increasing in e0 values with the increase in temperature while decreased with increase in frequency for polymer electrolyte system up to 10% of ammonium sulfate added. For values of addition greater than 10%, e0 is independent of both temperature and frequency. The ac conductivity is found to obey the power relation