The kinetics of o-cresol oxidation with ozone in acetic anhydride was studied. It was shown that o-cresol was acylated in acetic anhydride to give o-cresyl acetate. Ozone attacks the C=C bonds of the aromatic ring of o-cresyl acetate to give unsaturated peroxide compounds. The composition of the oxidation products alters when the ozonation is carried out in the presence of catalytic amounts of sulfuric acid. Along with the products of the destructive oxidation of the aromatic ring, the methyl group oxidation products appeared as the acyl derivatives o-acetoxybenzyl alcohol and o-acetoxybenzaldehyde, a form that is more stable toward the action of ozone (10%). The addition of manganese(II) acetate to the reaction mixture increases the methyl group oxidation selectivity to 75%. The mechanism of the ozone reaction with o-cresol in acetic anhydride that explains the obtained results is discussed.