The photoinduced degradation of an alkylphenol ethoxylate (APE) (Igepal CA 520) by Fe(III) in aqueous solution has been investigated. A complete characterization of the commercial product showed the presence of a mixture of compounds with various ethoxy and alkyl chain lengths. The photodegradation study was carried out with the major fraction of ethoxymers having an alkyl chain length of 8 carbon atoms and n ethoxy units E (C8PhEn). We have demonstrated that the Fe(III) sensitized degradation of this fraction occurs efficiently both at 365 nm and under sunlight. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of •OH radical formation. The primary step of the decomposition of Igepal involves the hydrogen abstraction on one carbon of the ethoxy chain. The shortening of the ethoxylated chain all along the degradation process was observed. The identified photoproducts are aldehyde ethoxylates, formate ethoxylates, and octylphenol that is a persistent product in the environment. The mechanism only involves attack by •OH radicals that are formed through photolysis of Fe(OH)2+. For prolonged irradiations, the total degradation of Igepal CA 520 and of the photoproducts is obtained. Consequently, the degradation photoinduced by Fe(III) could be an efficient method of APEs removal in water.