We report a study on the synthesis of cellulose-g-poly(methyl methacrylate)/organo-montmorillonite and its application in the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solution. The nanocomposite of cellulose-g-PMMA/OMMT was synthesized by using atom transfer radical polymerization. We investigated the effects of four reaction parameters on the grafting efficiency and percentage. The nanocomposite was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The effects of four parameters on the adsorption of 2,4-DCP were studied, which included pH, grafting percentage, adsorbate weight and the initial concentration of 2,4-DCP. Furthermore, adsorption isotherms and kinetics were investigated.