In this study, we reveal the capacity of imidacloprid (a neonicotinoid insecticide) to photoinduce the nitration and nitrosation of three aromatic probes (phenol, resorcinol, and tryptophan) in water. Using a gas-flow reactor and a NOx analyzer, the production of gaseous NO/NO2 was demonstrated during irradiation (300-450 nm) of imidacloprid (10-4 M). Quantum calculations showed that the formation of NOx proceeds via homolytic cleavage of the RN-NO2 bond in the triplet state. In addition to gaseous NO/NO2, nitrite and nitrate were also detected in water, with the following mass balance: 40 ± 8% for NO2, 2 ± 0.5% for NO, 52 ± 5% for NO3-, and 16 ± 2% for NO2-. The formation of nitro/nitroso probe derivatives was evidenced by high-resolution mass spectrometry, and their yields were found to range between 0.08 and 5.1%. The contribution of NO3-/NO2- to the nitration and nitrosation processes was found to be minor under our experimental conditions. In contrast, the addition of natural organic matter (NOM) significantly enhanced the yields of nitro/nitroso derivatives, likely via the production of triplet excited states (3NOM*) and HO•. These findings reveal the importance of investigating the photochemical reactivity of water contaminants in a mixture to better understand the cocktail effects on their fate and toxicity.