Ethylenediaminetetraacetic acid (EDTA) is often detected as contaminant in domestic wastewater (DWW) and liquid nuclear waste (LNW). Unfortunately, the existence of EDTA in DWW and LNW was proven to have an adverse impact on the conventional wastewater treatment efficiency. In this work, photocatalytic degradation of EDTA over commercial TiO2 (Evonik P25) has been investigated by using an irradiated environmental chamber with real-time diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectroscopy (MS) analysis. The degradation mechanism has been studied by varying different parameters, namely carrier gas, relative humidity, irradiation source and the loading of EDTA adsorbed on TiO2. Results showed a minimal degradation of EDTA under anaerobic conditions with production of ammonia and short-chained organic molecules (e.g. acetaldehyde). On the contrary, EDTA photooxidation took place under aerobic conditions with carbon dioxide and water as the main products. It is important to note that EDTA forms a visible absorbing complex with P25, which allowed photodegradation of EDTA under pure visible light (wavelength > 410 nm). Remarkably, the reaction mechanism was different when the system was irradiated with simulated solar light and near UV light.