Gallic acid is one of the most representative biorecalcitrant phenolic compounds present in cork processing wastewater. In this communication, chemical oxidation of gallic acid was studied by gamma irradiation as an advanced oxidation process. This technology turns out to be an advantageous tool for the degradation of gallic acid. The results obtained by UV-Vis and electrospray ionization mass spectrometry (ESI-MS) techniques are in agreement concerning the suitability of this technique to degrade gallic acid. ESI-MS and ESI-MS(2) monitoring of the non-irradiated and irradiated gallic acid solutions leads to the identification of the main intermediate products. Based on the overall results obtained a consistent mechanism of radiolytic degradation of gallic acid is proposed. The application of radiation as a tool to increase the biodegradability of wastewaters is an important issue from the perspective of Green Chemistry.