The mechanistic kinetic studies of oxidation of l-Alanine and l-Glycine by 1,3-dichloro-5, 5- dimethylhydantoin (DCDMH) in aqueous acetic acid medium in presence of H⁺ ions have been performed. The r ate of reaction is proportional to the first power of concentration of AA and DCDMH. The rate of reaction is enhanced by the increasing [H⁺ ] and percentage of acetic acid. The main product of the oxidation is corresponding aldehydes. H₂O⁺Cl has been assumed as prime reacting oxidizing species and proposed mechanism ruled out the involvement of free radicals. The thermodynamic parameters for the oxidation have been computed in the slow step of mechanism. The derived rate law was in good conformity with the mechanism.