Nanocomposite fibers made from polyacrylonitrile (PAN) containing carbon nanotubes (CNTs) and cobalt ferrite (CoFe2O4) nanoparticles were fabricated by electrospinning. The 1025 nm CoFe2O4 nanoparticles were made by a simple hydrothermal process. Characterization by X-ray diffraction confirmed that the CNTs and the CoFe2O4 nanoparticles were successfully incorporated into the PAN matrix. Scanning electron microscopy showed nanocomposite fibers with regular morphologies. Transmission electron microscopy revealed the internal distribution of the CNTs and CoFe2O4 nanoparticles. The nanocomposite fibers exhibited effective electromagnetic interference shielding attenuation of about 3.9 dB. Magnetic measurement using a vibrating sample magnetometer showed saturation magnetization of 4.7 emu g(-1), thus this property can be accurately tailored by adjusting the loading of CoFe2O4 nanoparticles. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics Engineers