A new approach to prepare surface-functionalized magnetic nanoparticles by synthesis of poly(methacrylic acid) (PMAA) coated maghemite nanoparticles in aqueous solution is reported. Maghemite (γ-Fe₂O₃) nanoparticles with an average diameter of 8 ± 2 nm were fabricated and subsequently coated with PMAA by emulsion polymerization. The FTIR study and thermal analysis confirmed the chemical adsorption of methacrylic acid on the maghemite nanoparticle surface, and suggested a symmetrical carboxylate bonding. The free carboxyl group of PMAA, which was verified by FTIR spectroscopy and zeta potential measurement, provided the site for immobilization of foreign molecules. The PMAA coated maghemite nanoparticles were demonstrated as potential magnetically targeted drug carriers by adsorbing an anti-cancer drug (carboplatin) via the ion–dipole interaction between CO₂⁻ of PMAA and carboplatin.