This paper reports the dielectric relaxation studies of carbon nanotubes loaded in polyester polymer matrix. The study was carried out in the frequency range between 100 Hz and 1 MHz at constant temperature, T = 300 K. The frequency dependence of the electrical data was treated in the frameworks of the impedance Havriliak-Negami formalism and by using the universal Jonscher power law. The imaginary and real parts of the dielectric permittivity change with concentration of the carbon nanotubes. This work consists in studying the influence of these nanoparticles on the dielectric properties, describing the electrical relaxation and the conduction mechanisms.