Hydrochloric acid doped polyaniline (PANI) nanofibers were synthesized by an interfacial polymerization with tetrachloride as the organic solvent and with a relatively higher aniline concentration. The doped PANI nanofibers were dispersed in cyclohexanone and the dispersion was mixed with solution of polyacrylate to prepare PANI nanofibers composite coatings. It was found that the yield of the doped PANI nanofibers can be as high as 23%, though a small amount of irregular shaped PAN[ particles and PANI nanofibers with relatively larger diameter were also obtained. The conductivity of the PANI nanofibers based composite coatings increased with the PANI nanofibers contents and a percolation threshold of 0.2 was demonstrated. The shielding effectiveness of the PANI nanofibers based coatings increased with PANI nanofibers loadings and shielding effectiveness as high as 63 dB can be achieved with PANI nanofibers loadings of 45%. POLYM. ENG. SCI., 48:355-359, 2008. (c) 2007 Society of Plastics Engineers.