In this work, the effect of controlling the morphology on the dielectric properties of triblock copolymers and their clay-containing nanocomposites was evaluated. Two different copolymers: polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) and SEBS grafted with maleic anhydride were used for that purpose. Morphologies with different degrees of intercalation, exfoliation and orientation were obtained and tested. At the highest state of dispersion, achieved at a clay loading equal to 5 wt%, 50% of clay nanoplatelets were individually dispersed and located within the soft domain of the block copolymer and a maximum of interfacial polarization and a minimum of dynamic mechanical damping factor were respectively exhibited. When the nanoclays were oriented, the dielectric loss due to nanoclays conductivity contribution was reduced up to 2 orders of magnitude at high temperatures and low frequencies and the AC short-term breakdown strength increased up to 45%. (C) 2015 Elsevier Ltd. All rights reserved.