The photocatalytic removal kinetics of fenitrothion at a concentration of 0.5mgl −1 in pure and natural waters were investigated in Fe(III)/H 2 O 2 /UV–Vis, Fe(III)/UV–Vis and H 2 O 2 /UV–Vis oxidation systems, with respect to decreases in fenitrothion concentrations with irradiation time using a solar simulator. Fenitrothion concentrations were determined by HPLC analysis. Furthermore, total mineralization of fenitrothion in these systems was evaluated by monitoring the decreases in DOC concentrations with solar simulator irradiation time by TOC analysis. It was shown that the degradation rate of fenitrothion was much faster in the Fe(III)/H 2 O 2 /UV–Vis system than the Fe(III)/UV–Vis and H 2 O 2 /UV–Vis systems in both pure and river waters. Consequently, the mineralization rate of fenitrothion was much faster in the Fe(III)/H 2 O 2 /UV–Vis system than in the other two systems. The high OH generation rate measured in the Fe(III)/H 2 O 2 /UV–Vis system was the key to faster degradation of fenitrothion. Increases in the concentrations of H 2 O 2 and Fe led to better final degradation of fenitrothion. These results suggest that the photo-Fenton reaction (Fe(III)/H 2 O 2 /UV–Vis) system is likely to be an effective method for removing fenitrothion from contaminated natural waters.