FePt nanoparticles doped with ∼12 at. % Zn were successfully synthesized using the polyol and thermolysis methods. Their chemical ordering to the face-centered tetragonal (L10) phase was found to occur at a remarkably reduced temperature of ∼324 °C. The nanoparticles annealed at 400 °C for 60 min were identified to be in a highly crystalline L10 phase, showing formation of the distinct FePt/Fe3O4 core/shell structure. Also, they demonstrated strong ferromagnetic characteristics due to the high crystallinity with the L10 phase and the exchange coupling between the FePt core and the Fe3O4 shell.