In this study, chemically modified iron oxide nanoparticles with super paramagnetic behavior and biodegradable properties were prepared through the reaction of a polymeric layer with surface hydroxyl functional groups of magnetic nanoparticles (MNP). For this purpose firstly, MNP was grafted with hexamethylene diisocyanate. Then, carboxymethyl cellulose which was modified with the hexamethylenediamine (mCMC) as a shell was coated and reacted simultaneously on MNP-grafted hexamethylene diisocyanate to form a polymeric core-shell (MNP/mCMC). The structural, morphological, thermal, and magnetic properties of the synthesized magnetite nanocomposite were confirmed by Fourier transform infrared spectrophotometer, thermal gravimetric analysis, X-ray diffraction, vibrating sample magnetometer, and scanning electron microscopy. The size of the resulting MNP/mCMC was approximately between 70 and 120 nm. Doxorubicin (DOX) as a model anticancer drug was used. The in vitro release of DOX from the MNP/mCMC was investigated and indicated that the release speed of the DOX could be well controlled. Release profiles of the DOX and its loading capacity were determined by ultraviolet-visible spectroscopy absorption measurement at lambda (max) 483 nm. The obtained results suggest that the prepared magnetite nanocomposite would be beneficial as a targeted anti-tumor drug carrier for pharmaceutical applications.