Monodisperse FePt nanoparticles with an average size of 4.11 nm were successfully synthesized via chemical co-reduction of iron acetylacetonate, Fe(acac)(3), and platinum acetylacetonate, Pt(acac)(2), by 1,2hexadecanediol as a reducing agent. Also (FePt)(87)Zn-13 nanoparticles with average size of 4.24 nm were synthesized using the same method. The structural and magnetic properties of the prepared samples were respectively studied by XRD, TEM and VSM. L1(0) FePt ordered phase is formed at lower annealing temperature by addition of Zn. The (FePt)(87)Zn-13 nanoparticles starts ordering after annealing at 400 A degrees C, whereas FePt nanoparticles at 400 A degrees C are still disordered alloys with superparamagnetic behavior. Additive Zn is very effective in decreasing the ordering temperature and enhancing the chemical ordering in (FePt)(87)Zn-13 particles, So that coercivity 5200 Oe was measured for (FePt)(87)Zn-13 nanoparticles annealed at 500 A degrees C, compared with 1800 Oe for samples without Zn. This reduction in ordering temperature significantly reduces FePt particle coalescence and loss in positional order.