The kinetics of oxidation of sulfanilamide by hexacyanoferrate (abbreviated as HCF) (III) ions in aqueous alkaline medium at constant ionic strength 0.01mol/dm3 and temperature 298°K has been studied spectrophotometrically. The reaction exhibit 1:3 stoichiometry and follows first order kinetics in [HCF (III)] and in [alkali]. The dependence of the rate on substrate concentration has been found to be of fractional order type. The ionic strength of the reaction mixture shows positive salt effect on the reaction rate. To calculate thermodynamic parameters the reaction has been studied at six different temperatures from 283°K to 333°K. Mechanism involving formation of complex between hexacyanoferrate and sulfanilamide has been proposed. Azoxybenzene-4, 4’-disulfonamide have been identified chromatographically and spectroscopically as the final product of oxidation of sulfanilamide. Based on the kinetic data and product analysis a reaction mechanism is proposed.