The presence of pharmaceutical compounds in the environment worries several researchers for several years since their existence in aquatic systems leads to major environmental problems. These compounds are a unique category of pollutants and considered emerging contaminants in water supply systems. They have been found in groundwater and even in drinking water at concentrations ranging from ng to µg/L. In the present work, we investigated the photochemical behavior of a sulfonamide antibiotic, namely sulfaguanidine (SGD) in aqueous solutions as a function of pH and we examined the inhibitory activity of photoproducts SDG against E coli BLSE and S. aureus using the disc diffusion method, determination of minimum inhibitory concentration and cell viability percentage. Quantum yields were measured at 254 and 302 nm during irradiation in absence and presence of oxygen). In aerated conditions, they were evaluated to 2.3 x 10−2 and 2.5 x 10−3 respectively. However, the degradation process is not completely inhibited in the presence of oxygen due to sulfaguanidine photoreactivity, which is in agreement with the involvement of the singlet as well as the triplet excited states. Several photoproducts were elucidated using liquid chromatography coupled with positive mode mass spectroscopy LC/MS/ESI +. For bacterial activity, these photoproducts shows more toxic that the Sulfaguanidine and exhibited a higher inhibitory activity against E coli and S. aureus cells.