Functionalization on carbon nanotube (CNT) was performed through the addition reaction between the initiators of atom transfer radical polymerization (ATRP) and CNT. The ATRP initiating groups transferred to the CNT surface with this reaction. The modified CNT then served as an ATRP macroinitiator for further modification. Both linear poly(styrene) and V-shaped poly(styrene-b-N-isopropylacrylamide) block copolymers were therefore covalently bound to the CNT surface. Characterization on the functionalized CNTs was performed with FTIR, Raman spectroscopy, and an X-ray photoelectron spectrophotometer (XPS). The functionalized CNTs exhibited good solubility in organic solvents. In addition, amphiphilic and temperature-responsive properties were observed with the CNTs functionalized with poly(styrene-b-N-isopropylacrylamide).