In this study, the effectiveness of Ce(III) ions adsorption in aqueous solution was investigated by modifying sodium alginate with magnetite nanoparticles. The magnetite nanoparticles were coated with sodium alginate (Alg-Fe3O4 nanoparticles), which was prepared by the co-precipitation method. The average size of the Alg-Fe3O4 nanoparticles was 13.70 nm. The optimum conditions for the adsorption process were found at pH 4, 4 hours of contact time and 0.15 g of adsorbent dosage in the batch condition. The adsorption process of Ce(III) ions followed the Langmuir isotherm. The kinetic data indicated that the intraparticle diffusion process was pseudo-second order with maximum adsorption capacity (qm) of 31.83 mg g−1. From this experiment, it can be concluded that Alg-Fe3O4 nanoparticles had good reusability shown by their adsorption-desorption ability using 0.01 M HNO3 as the desorption agent.