Multiwalled carbon nanotubes filled ABS (ABS/MWCNTs) composites were prepared via a method combined solution-blending with hot-press forming. Fractured cross-sectional surfaces of the ABS/MWCNTs composites were analyzed by scanning electron microscopy showing that MWCNTs were dispersed homogeneously in the ABS matrix. The volume resistivity of these composites was also analyzed and the percolation threshold was obtained at low filler loadings about 1–3 wt%. The Electromagnetic interference (EMI) shielding effectiveness (SE) of ABS/MWCNTs composites was investigated in 100–1500 MHz. It was found that SE of the prepared composites strongly depended on MWCNT loading. The highest EMI SE reaching 36 dB was observed for ABS/MWCNT composites containing 15 wt% of MWCNTs at 760 MHz.