A simple method to produce ferromagnetic FePt nanoparticle dispersions by thermal annealing of core/shell-structured FePt/MgO nanoparticles and removal of MgO in the presence of hexadecanethiol and oleic acid is reported. The ferromagnetic FePt nanoparticles have a room temperature coercivity of 1 T and magnetization of 56.4 emu per gram of FePt, and are suitable for single-particle magnetism studies and other magnetic applications.