ABSTRACT. Magnetic nanoparticles were prepared by the aqueous co-precipitation method. The magnetic nanoparticles obtained were characterized systematically through the use of an X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and a vibrating sampling magnetometer (VSM). The results revealed that the magnetic nanoparticles were spherical shaped with inverse spinel structure. The size of Fe3O4 and Nd-Co doped Fe3O4 magnetic nanoparticles were approximately 15 nm. Magnetic measurement revealed that the nanoparticles were super paramagnetic at room temperature. It was found that the magnetic response of the Fe3O4 increased when it was doped with Nd 3+ and Co 2+ . However, the magnetic response of the Fe3O4 decreased when it was doped with Nd 3+ or Ce 3+ or Cr 3+ or Ni 2+ .