Fe-Ni nanoparticles have been synthesized via a nonaqueous solution-phase approach using thermal decomposition of Ni(II) acetylacetonate and Fe(III) acetylacetonate in oleylamine without further reducing agents. The analyses of powder X-ray diffraction and transmission electron microscopy show that the as-synthesized Fe-Ni nanoparticles possess a face-centered cubic (fcc) crystalline structure and exhibit a polydispersed characteristic. The particle morphology and size distribution can be further controlled by introducing surfactants in the reaction system, and the final chemical composition also can be tuned to some extent by varying the initial molar ratios of metal precursors. Room temperature magnetic measurements reveal a ferromagnetic characteristic for the as-synthesized nanoparticles. An increased saturation magnetization has been observed with increasing Fe contents. (C) 2008 Elsevier B.V. All rights reserved.