The oxidation of cinnamic acid by N-bromoisonicotinamide was carried out in aqueous acetic acid medium. The reaction was catalysed by micelles cetyltrimethylammonium bromide (CTAB). The lone reaction shows first-order rate with oxidant and complex nature of the reaction was observed at its higher concentration. H₂O⁺Br was reported as an oxidant species, which attacks to the substrate with stoichiometric ratio 1:2. The rate of reaction increases with increase in binary composition of solvent. The proposed mechanism unconformities with the observed kinetic data and thermodynamic results have been discussed.