Polyaniline (PANI)-based magnetic nano-composites, with Mn-Zn ferrite nanoparticles as disperse phase, can be used for EMI shielding application in electronic devices. In the present work, PANIZMn0.8Zn 0.2Fe2O4 composites, having different PANI/Ferrite w/w ratios, were prepared under suitable synthesis conditions to avoid excessive dissolution of the ferrite and favor its dispersion into the polymeric matrix. The Mn0.8Zn0.2Fe2O 4 stoichiometry was selected because of its highest maximum magnetization value (55emu/g) and a susceptibility of 3.645. The ferrite average crystallite size was calculated as 10.6 nm using Scherrer's formula. XRD, HRTEM and SQUR) analyses confirmed the formation of the magnetic nanocomposite. As expected, the saturation magnetization in the nano-composites varied according to the PANI/Ferrite ratio, but without affecting the magnetic susceptibility of the ferrite.