We grafted polystyrene from the surface of single-walled carbon nanotube (SWNT) via Atom Transfer Radical Polymerization (ATRP). Direct electrophilic addition of chloroform and subsequent hydrolysis introduced hydroxyl groups to the surface of SWNT. ATRP initiators were attached to the SWNT by esterification of 2-chrolopropyl chloride with hydroxyl groups. Subsequent polymerization of styrene with CuCl / N,N,N',N',N"-pentamethyldiethylenetriamine catalyst yielded polystyrene grafted SWNT. Transmission electron microscopy analysis clearly showed that approximately 6 nm-thick polystyrene layer was uniformly formed on 1.2 nm diameter SWNT.