The kinetics of the decolorization reaction of methyl violet dye (MV) with the hydroxyl ion (nucleophile) was studied in the presence of cationic micelles of cetyltrimethylammonium bromide (CTAB). The reaction follows pseudo-first order kinetics. The rate constant depends on the surfactant concentration. CTAB micelles catalyze the overall reaction between the dye carbocation and the nucleophile. Quantitative analysis of the micellar data obtained has been done by applying positive cooperativity model of enzyme catalysis. For the dye under study, the value of n (index of cooperativity) has been found to be greater than 1. The catalytic effect has been explained in terms of hydrophobic and electrostatic interactions of various species present in the reaction systems. The addition of a counterion showed inhibitory effect on the reaction.