The superparamagnetic NiFe2O4 nanoparticles were synthesized using a hydrothermal technology through P123 sphere micelles as ‘nanoreactor’ in this work. Their morphologies, structures, surface properties and magnetism were characterized by FE-SEM, XRD, FTIR, and VSM, respectively. The nickel ferrite samples are nearly spherical and homogeneous nanoparticles with average size range of about 50-120 nm. They possess superparamagnetism at room temperature and higher saturation magnetization. X-ray diffraction (XRD) pattern confirms that the samples belong to the cubic crystal system with an inverse-spinel structure. Fourier transform infrared (FTIR) absorption spectrum indicates that the NiFe2O4 nanoparticles are stabilized by the P123 adsorbed on the surface of nanoparticles.