A CoFe2O4/polyacrylate nanocomposite was synthesized by in situ emulsion polymerization of an acrylic acid monomer in the presence of CoFe2O4 magnetic fluid. X-ray diffraction and FT-IR spectra confirmed the formation of the CoFe2O4/polyacrylate nanocomposite. Transmission electron microscopy images showed that CoFe2O4 nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite exhibited superparamagnetic behavior at room temperature under an applied magnetic field. The formation mechanism of the nanocomposite was investigated as well. (c) 2008 Elsevier Ltd. All rights reserved.