High-quality hydrophobic or hydrophilic ferrofluid based on magnetite ( Fe 3 O 4) nanoparticles can be synthesized by one-pot direct synthesis which involves thermolysis of Iron(III) acetylacetonate, Fe ( acac )3 in hydrophobic or hydrophilic stabilizing agent, respectively. The structure of the nanoparticles dispersed in the ferrofluid was studied using XRD, FTIR, XPS, and TGA analysis, while morphology and size of the nanoparticles were determined by TEM. The magnetic properties of the samples were measured using VSM and SQUID measurement. The results show that oleylamine (OM) and tri(ethylene glycol) (TREG) coated Fe 3 O 4 nanoparticles which are well stabilized in hydrophobic and hydrophilic ferrofluid, respectively, are relatively monodisperse, single crystalline and superparamagnetic in nature with the blocking temperature at around 100 K.