Iron oxide (Fe3O4) nanoparticles were synthesized by hydrothermal method. The chemical composition and morphologies of the as-prepared samples were characterized by X- ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Scanning Electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX). XRD confirms the presence of pure cubic phase Fe3O4 without any impurities. SEM image indicates the formation of agglomerated nanospheres. FTIR confirms the presence of metal-oxygen bond. The dielectric studies are also reported.