The attenuation of electromagnetic (EM) energy with polymeric nanocomposite foams is significant because the microwave energy is diminished by multiscattering of EM into microcellular structure. In this study, acrylonitrile butadiene styrene (ABS) and multi‐walled carbon nanotubes (MWCNTs) nanocomposite foams were fabricated via a chemical foaming in an injection‐molding process. It was demonstrated that the skin depth in foamed ABS/MWCNT specimens was fallen dramatically compared to their solid counterparts. The diminution of skin depth for foamed ABS/1 wt% of MWCNT nanocomposite was 21.7% compared to solid pure ABS. The reflectance of pure ABS was decreased by foaming but it was increased in foamed ABS/MWCNT nanocomposite. The absorption of microwave was improved by foaming and adding MWCNTs in ABS matrix. The utmost value of the experimental absorption shielding effectiveness (SEA. experimental), 14.26 dB, was found for the foamed ABS/1 wt% of MWCNT, holding pressure of 2 s and cooling time of 60 s F8, at 8.7 GHz. It was demonstrated that traveling path of EM wave was prolonged by the introduction of microcellular structure in ABS/MWCNT nanocomposite. Moreover, the contribution of MWCNT, holding pressure time, and cooling time to traveling path were achieved 76.7%, 8.5%, and 7.3%, respectively.
