Background: Gold (Au) Fe oxide core-shell nanostructure is a major class of nanoscale material that has attracted a considerable attention due to the biotechnological and biomedical applications and specific properties. Methods: Here we synthesized the magnetite nanoparticles (MNPs) with an average size of 10-12 nm in diameter using the chemical co-precipitation of Fe2+ and Fe3+ in strong alkaline material. Then, an Au coated Fe oxide core-shell nanocomposite with an average diameter of 18-20 nm was produced in the presence of sodium citrate as the reducing agent. The structures of Au shell and magnetic core (Au–Fe oxide) were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and fourier transformed infrared spectroscopy (FTIR). Results: Results showed that the NPs were agglomerate-free and shaped regularly, with a narrow sized distribution. The Au-coated Fe oxide NPs exhibited a surface plasmon resonance peak in the range of 500-650 nm with a remarkable peak at 550 nm. Conclusions: Immobilization studies with antibody (Ab) demonstrated that the Au Fe oxide core-shell nanostructure can be used to immobilize Ab, making them valuable for biomedical and biological applications.