Abstract A new analytical method based on Fourier transformed infrared spectroscopy (FTIR) using chemometric tools to treat spectral data is proposed to study the degradation of aqueous phenolic solutions by photo-Fenton process. Obtained results were validated by high-performance liquid chromatography (HPLC) taken as a reference method. First a discrimination of the different steps of phenol degradation was possible by applying a principal component analysis (PCA). Then a description of the reaction evolution was successfully made using MCR-ALS, a multivariate curve resolution method which has permitted to obtain the concentration profiles of phenol and its photoproducts. Kinetics of their formation and disappearance described with this new approach are in agreement with HPLC results. This methodology may be a good alternative to classical analyses for monitoring of the degradation reactions because a lot of data are recorded and treated simultaneously. It shows how species concentration varies over time, informing thus on the reaction mechanism because a structural identification of products is possible through pure extracted spectra.