Acrylonitrile based copolymers have a variety of industrial applications and attracted the attention of material researchers with increasing interest in recent years to study their electrical properties with respect to their homopolymers. The dielectric relaxation studies as a function of temperature and frequency of the applied field reveal the information about the nature of segmental motion in polymer chain. Radiation induced copolymerization of acrylonitrile with ethyl methacrylate (0.5 : 0.5 composition) was carried out in the aqueous medium at room temperature. The copolymer was characterized employing IR, 1H NMR and thermal studies (DSC). A systematic measurement of dielectric constant (ε) and dielectric loss (tan δ) were made as a function of frequency in the range 100 Hz -100 KHz and as a function of temperature in the range from room temperature to 180oC. Two types of relaxation peaks were observed above the glass transition temperature (Tg) and below the glass transition temperature of the copolymer. The peaks correspond to β and α relaxation respectively.