This research investigated effect of nitrate on the removal of profenofos (organophosphorous pesticide) in water using vacuum ultraviolet (VUV at wave lengths of 185 and 254 nm) and ultraviolet (UV at wave length of 254 nm). Nitrate concentrations (1, 10, and 50 mg/L) were varied. VUV degraded profenofos rapidly than UV (99% vs 80% reduction in 15 min). VUV with low nitrate concentration had higher profenofos degradation better than VUV without nitrate. This was due to more OH° formation. However, at high nitrate concentration, profenofos removal by VUV decreased. This could be because of the adsorption of VUV by nitrate molecules.