In this study, we have developed a facile route for the fabrication of a manganese dioxide–iron oxide–reduced graphite oxide magnetic nanocomposite (MnO₂–Fe₃O₄–rGO). The as-obtained nanomaterial (MnO₂–Fe₃O₄–rGO) was characterized using transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and Brunauer–Emmett–Teller surface area measurements. The MnO₂–Fe₃O₄–rGO composite shows extraordinary adsorption capacity and fast adsorption rates for the removal of uranium(VI) in aqueous solution. The influence of factors including the dosage of the MnO₂–Fe₃O₄–rGO composite used, pH of aqueous solution, and temperature were investigated. The thermodynamic parameters, including Gibbs free energy (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) for the process, were calculated using the Langmuir constants. The results show that a pseudo-second-order kinetics model can be used to describe the uptake process using a kinetics test. Our present study suggests that the MnO₂–Fe₃O₄–rGO composite can be used as a potential adsorbent for sorption of uranium(VI) as well as for providing a simple, fast separation method for the removal of uranium(VI) ions from aqueous solution.