The results of dielectric studies in semicrystalline poly (butylene succinate-co-butylene adipate) (PBSA) by means of dielectric relaxation spectroscopy from 163 to 353 K and in the frequency range of 0.056-17,800 Hz are reported. The subglass beta process is found to follow an Arrhenius temperature dependence, whereas the segmental alpha process follows a Vogel-Fulcher-Tammann temperature dependence. The higher temperature Maxwell-Wagner-Sillars (MWS) process was studied by applying the Bruggeman-Hanai equation, which helped to understand the underlying relaxation dynamics. The MWS process originates from the charge accumulation at the interface between the low-conductivity continuous medium and the high-conductivity dispersed particles. A three-phase model in which the medium comprises the crystalline and rigid amorphous phases (RAPs) and the particle comprises solely the mobile amorphous phases (MAPs) is required to explain the particle fraction variation with temperature. With increasing temperature, the MAP fraction increases at the expense of the RAP fraction within the continuous medium. POLYM. ENG. SCI., 51:386-390, 2011. (C) 2010 Society of Plastics Engineers