Here, nanocomposite particles with three domains including magnetite nanoparticles, poly(N-octadecyl methacrylate) (PODMA) or poly(N-octadecyl methacrylate-co-1-vinylimidazole) (P(ODMA-co-VIMZ)), and gold nanoparticles were prepared. Fe3O4 nanoparticles with narrow particle size distribution were prepared through a synthetic route in an organic phase in order to achieve good control of the size and size distribution and prevent their aggregation during their preparation. These magnetite nanoparticles, 5 nm in size, were then encapsulated and well-dispersed in PODMA and P(ODMA-co-VIMZ) matrices via a miniemulsion polymerization process to obtain the corresponding nanocomposite particles. The results revealed that Fe3O4 nanoparticles were encapsulated and did not migrate towards the monomer/water interface during polymerization. The resulting latex was used as a precursor for the adsorption of Au3+ ions on the surface of the polymeric particles and subsequent reduction to produce Fe3O4/P(ODMA-co-VIMZ)/Au nanocomposite particles. The morphology of the particles from each step was fully characterized by TEM and AFM, and the results of DLS analysis showed their size and size distribution. Measurement of magnetic properties illustrated the superparamagnetic characteristic of the products and it was observed that the encapsulation process and deposition of gold had no effect on the magnetic properties of the resulting particles. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013