A magnetic Fe3O4 montmorillonite composite was prepared and used for the separation of lead and cadmium from aqueous solutions. For this purpose, magnetite (Fe3O4) was generated by co-precipitation of FeSO4 and FeCl3 onto montmorillonite. The effects of various experimental parameters such as pH of the solution, amount of sorbent, initial concentration of analytes, and contact time on the sorption efficiencies of lead and cadmium ions were investigated and optimized by applying a batch technique. The concentrations of analytes were determined by high resolution continuum source flame atomic absorption spectrometry. The maximum adsorption occurred at pH 2.0. The adsorption capacity of Fe3O4 a montmorillonite composite was 5 mg g(-1) Pb and 2 mg g(-1) Cd. The quantitative retention in acidic medium was an advantage for the removal of metals from acidic water samples. Under optimized conditions, lead and cadmium were quantitatively removed from wastewater (between 95% and 98%) in a contact time of less than 5 min. The results showed that Fe3O4 montmorillonite can be efficiently used for the removal of lead and cadmium from aqueous solutions.