An electromagnetic interference (EMI) shielding material based on the composite of BaFe12O19, polyaniline (PANI) and multi-walled carbon nanotube (MWCNT) was proposed. The constituents of the composite were brought together through mechanical mixing and the in-situ polymerization of aniline on the BaFe12O19 and MWCNT surfaces. A series of composite with different MWCNT wt loadings (0, 5, 10, 15, 20 and 25wt) was prepared, and its effect on the EMI shielding performance was investigated. X-ray diffraction analysis was performed on all synthesized composites to confirm the phase formations. FESEM micrographs reveal the PANI particle formation on both BaFe12O19 and MWCNT surfaces. Electromagnetic measurements were done by using a rectangular waveguide connected to a network analyser to obtain the permeability, μr, permittivity, εr, and shielding effectiveness (SEA and SER). The increase in the MWCNT loading results in the enhancement of the composite�s shielding performance to a certain limit. Optimum EMI shielding performance is shown by sample PBM4 (20wt MWCNT) with SER and SEA values of 5.14 dB at 8.2 GHz and 36.41 dB at 12.4 GHz, respectively. The influence of different MWCNT loadings (0, 5, 10, 15, 20 and 25wt) on the EMI shielding performance of a composite consisting of BaFe12O19, polyaniline (PANI) and multi-walled carbon nanotube (MWCNT) were investigated. © 2016, Electromagnetics Academy. All rights reserved.