Magnetic Fe3O4 nanoparticles were synthesized, surface modified with an amino-terminated silane coupling agent, 3-aminopropyltrimethoxysilane (APTMS), and characterized by Fourier transform infrared spectroscopy (FT-IR), field scanning electron microscopy (FESEM), and X-ray diffraction (XRD). A copolymer of methyl methacrylate (MMA) and maleic anhydride (MA), poly(MMA-co-MA), was synthesized by radical polymerization and transformed into magnetic nanocomposite (MNC) by chemical immobilization of APTMS-Fe3O4 with the anhydride groups of poly(MMA-co-MA) chains. The MNC was characterized by FT-IR, XRD, FESEM, TEM, and atomic force microscopy (AFM) and used for the removal of metal ions from water. Various factors influencing adsorption capacity such as contact time, absorbent dosage, pH, and initial concentration of ions were investigated. The adsorption kinetics showed a pseudo-second-order rate law, indicating chemical sorption as the rate-limiting step mechanism. Sorption of metal ions to MNC agreed well with the Langmuir adsorption model with the maximum adsorption capacity of 90.09, 90.91, 109.89, and 111.11 mg g(-1) for Co2+, Cr3+, Zn2+, and Cd2+, respectively.