Core-shell type magnetic nanocomposites based on Beta zeolites and magnetite (Fe3O4) nanoparticles have been synthesized under hydrothermal conditions. It has been revealed that the magnetic nanocomposites obtained have a high sorption capacity for the organic dye methylene blue. It has been found that the maximum absorption of methylene blue on a Beta-Fe(3)O(4)sample is 186 mg/g, with the adsorption equilibrium being reached within 90 min. The mechanisms and characteristic parameters of the adsorption process have been analyzed using the Langmuir and Freundlich isotherm models. Sorption kinetic curves have been evaluated using the diffusion model and the pseudo-first and pseudo-second order models. The results indicate that the adsorption process has a chemisorption nature, since it obeys the pseudo-second-order rate law.