The kinetics and mechanistic aspects of the oxidation of two beta-lactam antibiotics (A), ampicillin and flucloxacillin, by alkaline hexacyanoferrate(III) (HCF(III)) were examined using spectrophotometry at a fixed temperature. The oxidation reactions showed a 1:4 (A: HCF(III)) stoichiometry. The reaction kinetics were found to follow first-order dependence for the oxidant and fractional first-order dependence for [A] and [OH−]. The enhancement of the ionic strength and dielectric constant was found to increase the oxidation rates. Free radical tests of the reactions showed positive results. The addition of HCF(II) as a predicted oxidation product did not considerably change the oxidation rates. Under the same experimental conditions, the oxidation rate of ampicillin was found to be slightly lower than that of flucloxacillin. The acquired oxidation products were recognized using spot testing and Fourier transform infrared spectra. A conceivable oxidation mechanism was suggested. A derived rate law expression was found to be consistent with the experimental results. The activation parameters were assessed and discussed.