The magnetic Cs adsorbent functionalized with hierarchical titanium-ferrocyanide were fabricated for the highly efficient magnetic removal of radioactive cesium from water. The new magnetic Cs adsorbent has a core–shell structure that comprises a Fe3O4 core, an interlayer of SiO2, and a titanium-ferrocyanide-shell with hierarchical nanostructure. At first, the magnetic Fe3O4 nanoparticles synthesized via a hydrothermal reaction were coated with SiO2. Then, TiO2 were coated on the surface of SiO2 coated magnetic nanoparticles. Finally, the hierarchical titanium-ferrocyanide composed of 2-dimensional TiFC flakes was fabricated on the surface of core-shell MNP@SiO2@TiO2 microparticles using a TiO2 sacrificial template via a simple reaction with potassium ferrocyanide (FC) based on the Kirkendall-type diffusion. The resulting magnetic Cs adsorbent shows higher adsorption capacity of 416 mg/g than other magnetic Cs adsorbents (below 200 mg/g) because of the increased effective surface area of hierarchical titanium-ferrocyanide. Therefore, our Magnetic Cs adsorbent functionalized with hierarchical titanium-ferrocyanide has excellent potential for the treatment of various 137Cs-contaminated sources.