In the present study, carbonyl iron powder (CIP)-embedded carbon fiber-reinforced polymer (CFRP) composites were fabricated as lightweight electromagnetic interference (EMI) shielding composites. Four different CIP contents (e.g., 0%, 100%, 200%, and 300% by mass of epoxy resin) were added to fabricate the composites, and the effects of the incorporated CIP contents on the electrical characteristics and EMI shielding capability of the composites were investigated by means of AC conductivity, reflection and absorption of EM wave shielding tests, and by calculating the permittivity and permeability values. These outcomes showed that the EMI shielding capability was improved when increasing the incorporated CIP content. The results were analyzed using microstructural images taken via a FE-SEM and by EDS observations, which showed that the Fe-atomic components increased with the addition of CIP, thus improving the EMI shielding capability. In addition, the fabricated CIP-embedded CFRP composites were coated onto cement mortar and the applicability of these coated composites as EMI shielding composites in structures was examined. Shielding effectiveness exceeding 50 dB was noted, suggesting a potential of utilizing the fabricated CIP-embedded CFRP composites as EMI shielding composites in the structures.