Blends of polyamide 6/polystyrene (PA6/PS) (50/50 wt./wt. %) were loaded with different concentrations of boron carbide (B 4 C), (0, 5, 10, 15, 20 and 30 wt./wt. %) separately for EMI shielding. The effects of different weight fractions of fillers on thermal, electrical, as well as, mechanical behavior of the prepared composites were investigated. Thermal stability and hardness (shore D) of composites are studied. Addition of B 4 C enhances thermal stability of the prepared composites which attributed to the increase in physical and chemical cross-linking points, also to the interactions between the filler and polymer blend. Confirmation of thermal stability was done by determining the activation energy (E a) for the thermal decomposition of all composites. Characterization of the prepared composites was done using SEM. With B 4 C-loaded PA6/PS blend composites, samples of 2 mm thick, SE values of 5-36 dB were achieved, satisfying the requirement for common commercial applications.