Micellar effect upon nucleophilic substitution reactions between hydroxide ions and tri-2-methoxy phenyl phosphoramide (2-MPPA) in presence of cetyl trimethyl ammonium bromide (CTABr) has been examined in buffered medium at pH 8-10. The first order rate constant (Kψ) are increased with the concentration of the surfactant can be analysed in terms of Bromide ions in micellar pseudophase, which occur readily by aqueous CTABr and calculated second order rate constants.