Dispersed NiFe2O4 nanoparticles are synthesized through thermal decomposition of mixed-metal (Ni2+Fe 3+)-oleate complex in the presence of high boiling point organic solvent 1-octadecene with oleic acid, by tuning the mixed-metal (Ni 2+Fe3+)-oleate complex precursor and the temperature. Oleic acid is used as a surfactant, capped on the surface of the particles, which assists the particles to disperse in hexane. The as-synthesized NiFe 2O4 nanoparticles have a cubic spinel structure as characterized by x-ray diffraction. The ferrimagnetic nature of these nanoparticles is conformed from the field dependent room temperature magnetization curves measured using vibrating sample magnetometer. The saturation magnetization of these nanoparticles strongly depends on the particle size which can be tuned by the mixed-metal (Ni2+Fe 3+)-oleate complex precursor concentration and the synthesis temperature. Transmission electron microscope images show that the particles are nearly monodispersed at high synthesis temperature. © 2013 American Institute of Physics.