The kinetics of the ozonation of four phenolic aldehydes is investigated from ozone absorption experiments in a semi-continuous reactor. After the evaluation of the stoichiometric ratios for the individual reactions between ozone and each aldehyde, the single oxidation of vanillin aldehyde (4-hydroxy-3-methoxy benzaldehyde) by ozone is performed in a first stage. The influence of the operating variables on the degradation process is established, and the application of a mass transfer with chemical reaction model based on the film theory leads to the determination of the reaction orders and kinetic rate constants. The experimental absorption rates obtained agree well with those calculated theoretically. In a second stage, a mixture of protocatechuic aldehyde (3,4-dihydroxybenzaldehyde), p-hydroxybenzaldehyde, vanillin aldehyde and syringaldehyde (4-hydroxy-3,5-dimethoxy benzaldehyde) is ozonated under different experimental conditions. The kinetic study is performed by means of a competitive method that takes vanillin aldehyde as reference compound. The application of that model allows the determination of the kinetic rate constants for each aldehyde, which are correlated as a function of pH and temperature. The results obtained support the fact that the kinetic regime of absorption is fast and pseudo-first order with respect to ozone, a condition required by the competitive method to be used.