In this work, the electrical characteristics of nanocomposites obtained by dispersing multi walled carbon nanotubes in epoxy resins are investigated. The morphological characterization, samples preparation and dispersion of MWCNTs inside the resin are discussed. The complex permittivity of nanocomposites (in the range 100 kHz-12MHz and 1-18 GHz) is measured and its value discussed in the light of filler percentage and MWCNTs characteristics. The shielding effectiveness (SE) is computed for different weight percentage of MWCNTs.