Diazinon is a moderately persistent organophosphorus pesticide used to control a variety of insects in both household and agricultural because of its inhibition ability of acetylcholinesterase in the vast majority of insects. So far, diazinon residues have been found in many agricultural products and affecting a wide range of non-target organisms proving harmful to human and aquatic environments. The aim of this study was to evaluate the sonophotocatalytic degradation of diazinon, in aqueous solution, using iron doped TiO2 nanoparticles. Iron doped TiO2 nanoparticles were synthesized under mild hydrothermal conditions (T = 110 degrees C, p = autogenous, t = 12 h). The systematic characterization of nanoparticles was determined using Powder X-ray Diffraction, Fourier transform infrared and Scanning electron microscopy techniques. Moreover, the effects of different parameters such as pH, nanocatalyst dosage, initial diazinon concentration, and Fe doping concentration on the degradation efficiency of diazinon were investigated. The degradation efficiency of diazinon in each sample was measured using a UV-Vis spectrophotometer (lambda(max) = 247 nm) at different time intervals. The results demonstrated that nanoparticles were successfully synthesized and the forms of the nanoparticles synthesized" are quite similar to each other and approximately pseudo-spherical. The optimum conditions for sonophotocatalytic degradation of the diazinon obtained were: pH 5.5, nanocatalyst dosage = 0.4 g/1, initial diazinon concentration = 30 mg/1, dopant percentage = 1.5% and contact time = 100 min. Under optimal conditions, the sonophotocatalytic degradation efficiency of diazinon was 85%. In addition, the results showed that the iron doped TiO2 nanocatalyst, UV irradiation and US irradiation had a positive effect on the sonophotocatalytic degradation of diazinon. The maximum degradation values of diazinon achieved for separate applications, namely, iron-doped TiO2, UV irradiation, and US irradiation was 30, 36, and 19% respectively.