We report a general strategy for functionalizing the sidewalls of carbon nanotubes (CNTs), which is based on electrophilic substitution reactions on phenylated CNTs. By using this strategy, four new functionalized CNTs were prepared, including diphenyl ketone, benzenesulfonyl chloride, benzyl chloride and thiophenol modified CNTs. The benzenesulfonyl chloride and benzyl chloride functinalized CNTs could serve as novel initiators for surface-initiated atom transfer radical polymerization. The thiophenol modified CNTs were used in immobilizing Pd nanoparticles on the CNT surface, and the CNT/Pd hybrid produced exhibits good catalytic efficiency for the electrochemical oxidation of methanol.