Abstract Annealed iron-platinum (FePt) is ferromagnetic in a nanoscale regime which is necessary for energy and data storage, whereas the as-synthesized form of FePt-based nanoparticles exhibits superparamagnetism useful for biomedical applications. In this study, as-synthesized nanosuspensions from the reaction of Pt(acac)₂ with Fe(acac)₃ and Fe(hfac)₃ are compared. X-ray diffraction (XRD) peaks for both samples are assigned to the FePt₃ phase. As shown by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), nanoparticles synthesized by using Fe(acac)₃ have a smaller average diameter, but larger polydispersity index and particle agglomerations. On the other hand, the nanoparticles synthesized by using Fe(hfac)₃ can self-assemble into a longer range of patterned monolayer. Dynamic light scattering (DLS), measuring the size of cluster of nanoparticles as well as oleic acid and oleylamine at their surface, confirms that larger agglomerations in the sample were synthesized by using Fe(acac)₃. In addition to the size distribution, magnetic properties were influenced by the composition of these nanoparticles.