Conductive rubber-based composites were derived from EVA, EPDM, and 50/50 EVA/EPDM blend filled with carbon black and short carbon fiber (SCR The electromagnetic interference (EMI) shielding effectiveness and return loss were studied. The measurements of shielding effectiveness (SE) of the composites were carried out in two different frequency ranges: 100-2,000 MHz and 8-12 GHz (X-band). It has been observed that the shielding effectiveness of the composites is frequency dependent and increases with increasing frequency. The increasing of filler loading also enhances the SE of the composites. It is also found that 50/50 EVA/EPDM blend systems have higher shielding effectiveness than pure EVA and EPDM SCF-filled composites. The correlation between shielding effectiveness and bulk conductivity of various composites is also discussed.