The effect of acoustic cavitation on the carboxylation of carbon nanotubes (CNTs) at room temperature was studied and compared with the conventional reflux process. Due to the dispersion caused by the shockwave and jet damage from the collapse of microbubbles, and the energy imparted by intense local temperature and pressure, a positive correlation between the amount of attached functional groups and sonication time was observed. The use of ultrasonication for the carboxylation of CNTs demonstrated merits over the conventional reflux method in the form of significantly higher and easier recovery of reacted samples, improved carboxylation yield with simpler equipment setup. (C) 2012 Elsevier B.V. All rights reserved.