The effect of gamma irradiation on physical and electrical properties of polyethylene oxide (PEO)-based nano-composite polymer electrolyte films was investigated. The structural change induced and the reduction in crystallinity of the electrolyte film before and after irradiation were confirmed by FTIR spectra and X-ray diffraction studies. Microstructural studies carried out by scanning electron microscope technique reveal significant change in the surface morphology on irradiation. The bulk conductivities of the films were studied using standard impedance spectroscopic technique. A maximum ionic conductivity of 1.717 × 10−4 S cm−1 was observed for 40 kGy radiation dose, which is higher than earlier reported studies. Ion dynamics behaviour of the films was studied by frequency-dependent conductivity measurements which follow universal power law. The dielectric constant tends to be higher for films with higher lithium ion conductivity.