Background: Heavy metals, even at low concentrations, are harmful to human health and environment. Cadmium as a heavy metal is highly toxic and can cause serious threat to living organisms. This research was designed to evaluate the adsorption potential of modified magnetic iron nanoparticles by 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol ligand for the removal of cadmium ions from water solutions. Methods: This study was conducted in Ilam Branch, Islamic Azad University, Iran, in 2014. Modified magnetic iron nanoparticle was used as adsorbent for the removal of cadmium from aqueous solution. In batch extraction, the effects of parameters like pH of sample solution (3.0-11.0), initial metal concentrations (50-300) mgL-1), contact time (1.0-10 min) and adsorbent dose (10.0-60.0 mg) were studied on the adsorption process. Modified magnetite nanoparticle was presented as the adsorbent for the removal of cadmium ions from aqueous samples and later was confirmed by flame atomic absorption spectrometry. Results: The adsorption of cadmium ions on modified magnetite nanoparticles strongly depends on pH. The experimental isothermal data were analyzed using the Langmuir and Freundlich equations. The removal process followed the Langmuir isotherm. Maximum adsorption capacity for the adsorption of cadmium ions by the sorbent was 24.09 mgg-1. Conclusion: The method was successfully applied to adsorption of cadmium in water samples with satisfactory results. Other advantages include high capacity, good stability and fast adsorption kinetics. High pre-concentration factor was obtained easily by this method (120) and low analysis cost.