Separation of Sm3+ from a dilute solution via conventional solvent extraction is often plagued by emulsion and third phase formation. These problems can be overcome with functionalized magnetic nanoparticles that can capture the target species and be separated from the raffinae phase rapidly and efficiently on application of a magnetic field. Magentic silica nanoparticles (Fe2O3/SiO2) were synthesized by a modified Stober method and functionalized with carboxylate (Fe2O3/SiO2/RCOONa) and phosphonate (Fe2O3/SiO2/R1R2PO3Na) groups to achieve high adsorption capacity and fast adsorption kinetics. The adsorbents were characterized by X-ray diffraction analysis, transmission electron microscopy, BET measurements, magnetization property evaluation, Fourier infrared spectroscopy, and thermogravimetric analysis. Equilibrium adsorption of Sm3+ on Fe2O3/SiO2/RCOONa particles was attained within 10 min and within 20 min on Fe2O3/SiO2/R1R2PO3Na nanoparticles. The kinetic data were correlated well with a pseudo-second-order model. Adsorption capacities of Fe2O3/SiO2/RCOONa and Fe2O3/SiO2/R1R2PO3Na were 228 and 180 mg/g, respectively. The recovery of the adsorbed Sm3+ using 2 mol/L HCI as desorption agent was evaluated. The adsorption mechanism is discussed based on FTIR analysis, carboxylate group/Sm3+ molar ratio, phosphonate group/Sm3+ molar ratio, and pH. The adsorbents show significant potential for Sm3+ recovery in industrial applications.