In this paper, magnetic keratin as a new nanocomposite was synthesized to overcome the handling and separation problem coexist with keratin nanoparticles (KNPs). The nanocomposite was prepared by in-situ synthesis of Fe3O4 in a dilute aqueous solution of KNPs of 0.5 g/L using the co-precipitation method. The synthesized nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). Magnetic field implementation and XRD pattern confirmed that the nanocomposite was magnetic. The presence of amide I and II as well as Fe-O band in the FTIR analysis of the nanocomposite structure indicated that both Fe3O4 and keratin were present in its structure. Transmission electron microscopy (TEM) images showed that the nanocomposite had a mean diameter of 15.0 nm and a core-shell structure with a mean shell thickness of about 1.3 nm. Based on TGA, it was concluded that only 8.4% of the nanocomposite weight was assigned to keratin. Additionally, the vibrating sample magnetometry (VSM) analysis revealed that the magnetization of the nanocomposite was a little lower than Fe3O4. The nanocomposite also showed a good capability of Cu(II) adsorption as compared to the naked Fe3O4 and KNP by removing up to 98% of Cu(II) from aqueous solution. (C) 2018 Elsevier B.V. All rights reserved.