The pristine nanosilica particles were melt-blended with a model low-density polyethylene-ethylene vinyl acetate thermoplastic elastomers (TPE) system by varying the sequence of addition and nanosilica contents. Bis[3-(triethoxysilyl)propyl] tetrasulfide (Si-69) was used to improve the state of dispersion of nanosilica particles in one of the compositions. The dielectric properties of the TPE systems are influenced remarkably by loadings of silica, variation of sequence of addition of ingredients during mixing, addition of Si-69, and controlled electron beam irradiation. The effects of interfacial and orientation polarization on the permittivity and the loss tangent were studied by dielectric analyses. These were correlated with the structures of various nanocomposites. An attempt has also been made to support the dielectric results by volume resistivity measurements, measurements of breakdown voltage, and swelling-deswelling kinetic results. POLYM. ENG. SCI., 50:730-738, 2010. (C) 2009 Society of Plastics Engineers