<p>Silicon dioxide (SiO₂) nanoparticles were incorporated in the films of polymer blend electrolytes of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) doped with ammonium iodide salt by using solution casting method. The functional groups present in PVA/PVP/NH₄I and SiO₂ polymer blend were found through Fourier transform infrared studies. Amorphous nature of films was confirmed by the analysis of X-ray diffraction and also observed that amorphous nature has been increased by adding nanofiller. SEM micrographs are used to find the surface morphology and found that surface becomes smooth with the addition of nanofillers. The ionic conductivity and dielectric behavior has been investigated using impedance spectroscopy at various temperatures and found that the base matrix dielectric properties were improved with the addition of nanofiller silicon dioxide. The optimized sample, containing 0.5 wt% SiO₂, achieved a maximum conductivity of 3.9×10 ⁻⁴ S/cm at room temperature. Ionic conductivity values and dielectric properties for all prepared films gradually increased with temperature. And also it was observed that the dielectric properties were increased with temperature. Glass transition temperature of the polymer nanocomposites was calculated from the DSC thermograms and observed the falling off <i>T</i>_<i>g</i> value with the addition of SiO₂.</p>