In the present work, magnetic nanocomposites of the multi-walled carbon nanotubes (MWCNTs) decorated with magnesium ferrite (MgFe2O4) nanoparticles were synthesized successfully by citrate-gel method. The shape, structure, size, and properties of the as-synthesized sample were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction pattern (XRD), transmission electron microscope (TEM), vibrating sample magnetometry (VSM), and AC susceptibility measurements. The results showed that MWCNTs and MgFe2O4 coexisted in the nanocomposite and a large number of the high purity magnesium ferrite MgFe2O4 nanoparticles were attached on the surface of the MWCNTs. The hysteresis loop of the MgFe2O4/MWCNTs nanocomposites showed that the nanocomposites were superparamagnetic with the saturated magnetization of 11.79 emu/g, and the coercive of 49Oe.