PS+Fe₃O₄-based nanocomposites were fabricated by combining solution casting and hot pressing methods. SEM image revealed the presence of microvoids and pores on the volume of the nanocomposites. This microstructure indicates that the incorporation of Fe₃O₄ nanoparticles altered the morphology of the polymer matrix. Dielectric measure-ments performed in the 50 kHz–1 MHz frequency range showed that the addition of Fe₃O₄ increased the polarity of the composites and modified their relaxation behavior. In particular, the PS+10%Fe₃O₄ nanocomposite exhibited a weak frequency dependence of dielectric permittivity, while the dielectric loss tangent of all filled samples was higher than that of neat PS. These results demonstrate that Fe₃O₄ nanoparticles strongly influ-ence the interfacial polarization and dielectric response of PS-based nanocomposites.