Carbon nanotubes [CNTs] have excellent electrical, mechanical, optical and thermal properties. However, efficient dispersion of CNTs in any medium requires their functionalization. In this work, CNTs prepared from the catalytic process have been functionalized under three different conditions using the same acid oxidizing media. The effect of the reaction conditions on the CNTs, in terms of the extent of covalent functionalization has been determined by employing SEM, FTIR, XRD, Zeta meter, UV, Oxygen percentage analysis, Boehm’s titration and visual dispersion as the characterization techniques . Results show that CNTs functionalized by reflux in the oxidizing acid are the best dispersed.