Abstract More than 20 wt.% of grape production typically becomes waste during wine production. Grape seed oil can be extracted from this winery by-product through pressing or solvent extraction. This oil constitutes an economic alternative for valuation of by-products obtained from wine manufacturing in the Spanish region of Castilla-La Mancha. Furthermore, epoxidised vegetable oils have become one of the main intermediates for synthesizing different biomaterials. The most extended method for epoxidation is using peracids generated in situ , and many studies have investigated the influence of different variables such us reaction temperature and time, type and amount of catalyst, etc. However, a complete kinetic model able to predict reaction by-products has not yet been developed. In this work, the in situ epoxidation of grape seed oil (iodine value of 141.52 g I 2 /100 g) with aqueous hydrogen peroxide and acetic acid in presence of an acid catalyst was performed, with optimal reaction conditions of 90 °C and 60 min. Also, a general epoxidation reaction mechanism has been proposed. We propose a kinetic model able to predict the formation or depletion of different species in the process. The dependence of kinetic rate constants on temperature was evaluated through the Arrhenius equation. The activation energy for the epoxidation reaction of grape seed oil was 7.30 kcal/mol. The obtained results, particularly the proposed kinetic model, will play an important role in developing a safer and more sustainable epoxidation process, minimizing energy consumption and facilitating scale-up.