In the present study, it has been attempted an innovated application, i.e., electromagnetic interference shielding material, to reutilize copper smelter slag, aiming at an alternative high value added product. Notably, a proof-of-concept experiment with an addition of a 45 wt.% of copper slag alone to the cement matrix boost the shielding effectiveness (SE) to approximately 7-8 dB in the 500 MHz-1.5 GHz frequency range, highlights the incident electromagnetic wave has been weakened by approximately 60 pct. This phenomenon is attributed to the iron silicate, fayalite, and magnetite embedded in the sample mixture serve as magnetic and dielectric loss absorbent, deriving from the copper slag. Copper slag with low value application, shows its competitive economic and social advantages as candidate infill for electromagnetic interference shielding materials.