In this work, the influences of gamma irradiation on the electrical and mechanical properties of the epoxy nanocomposites were studied. The exfoliation characteristics of epoxy nanocomposite material analyzed through TEM studies. It is shown that the impact and flexural strength of the material is high with epoxy nanocomposites and gets reduced with the gamma-irradiated specimen. The AC breakdown strength of the epoxy nanocomposites is high compared with the base epoxy resin. It is also observed that a reduction in permittivity and tan(d) of epoxy resin added with 1 wt % of nanoclay. Increase in percentage of clay shows increase in permittivity and tan(d). Gamma irradiation of epoxy nanocomposite material shows increase in permittivity. The volume resistivity of the material is high with epoxy nanocomposite and is less with gamma-irradiated specimen compared with virgin specimen. The impact strength and flexural strength indicates correlation with breakdown strength of the material. It is observed that the increase in applied voltage shows an increase in magnitude of the charge density in the insulation structure. With the gamma-irradiated specimen, the charge density (for the applied electric field) is less compared with the virgin specimen. Electric field analysis indicates that the electric field is uniform in the bulk volume of the epoxy nanocomposite material. The rate of charge decay is high with gamma-irradiated specimen compared with virgin specimen. It is realized that material with lower resistivity has faster decay of stored charge. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012