A method for obtaining a new magnetic nanocomposite Fe3O4@SiO2@Mg/AlFe-LDH with the core/shell structure is described. The procedure for the synthesis of the nanocomposite includes three steps: preparing magnetite nanoparticles, coating the surface of the obtained magnetic nanoparticles with silica, and in situ growing Mg/AlFe-LDH on the Fe3O4@SiO2 surface. Samples obtained at each synthesis step have been characterized using X-ray diffraction analysis and transmission electron microscopy. It has been proved that the layered double hydroxide (LDH) particles "grow" on aggregates of magnetic Fe3O4@SiO2 core/shell nanoparticles and have the so-called "flower-like" morphology.