A novel combination of nanoparticles of rare earth oxide ceria (CeO2) dispersed in polyethylene oxide (PEO)/polyethylene glycol (PEG) blend polymer doped with cation donor salt lithium perchlorate (LiClO4), and ethylene carbonate (EC) nanocomposite polymer electrolyte (NCPE) was prepared by standard solution casting technique. The X-ray diffraction (XRD) patterns reveal that the amorphous nature of the nanocomposite has been increased considerably on dispersion of nanofiller. The complexation was further confirmed by Fourier transform infrared (FTIR) analysis. The impedance spectroscopy technique was used to measure the ionic conductivity and activation energy of the nanocomposite electrolytes. The maximum ambient temperature conductivity of 1.18 × 10−4 Scm−1 was obtained for the nanocomposite of 68 % PEO, 16 % PEG, 11 % LiClO4, 5 % EC, and 1 % CeO2 by weight percentage. The ac conductivity follows the universal power law. The variation of dielectric permittivity, dielectric loss, and modulus spectra with frequency and temperature was consistent with conductivity. The activation energy calculated from temperature-dependent imaginary modulus well coincides with that of conductivity. The loss tangent ascertains the presence of conductivity relaxation and the minimum relaxation time for highest conducting electrolyte.