The oxidative cleavage of diethylene glycol by bromate ion has been studied in hydrochloric acid medium in the temperature range 298-313 K. The rate of the reaction is dependent on the first power of the concentration of diethylene glycol and bromate ion. The reaction rate increases with increase in H+ concentration in the range (0.1 - 1.0) mol dm-3 and reaction is first order with respect to [H+]. The reaction has been shown to occur with the formation of an unstable bromate ester which decomposes to the reaction product in one step two-electron transfer process. Formaldehyde has been identified as the oxidation product of diethylene glycol. The activation parameters of the oxidative cleavage of diethylene glycol have been evaluated.