This study assessed the effects of caffeic acid phenethyl ester (CAPE) on diazinon-induced lung injury. A total of 40 Wistar Albino male rats were divided into three groups. Group 1 received only corn oil, group 2 received 300 mg/kg diazinon in corn oil, group 3 received 300 mg/kg diazinon in corn oil plus10 mu mol/kg CAPE. All solutions were administered by oral gavage. Intraparenchymal infiltration, alveolar and bronchial hemorrhage, emphysematous changes, and intraparenchymal vascular congestion and thrombosis were evaluated histopathologically in lung specimens and the severity of each was rated by a semiquantitative scoring system. Intraparenchymal infiltration was significantly more severe in group 2 and group 3 than in group 1, but similar in groups 2 and 3. Alveolar and bronchial hemorrhage, emphysematous changes, and intraparenchymal congestion and thrombosis were significantly more severe in group 2 and group 3 than in group 1 and significantly less severe in group 3 than in group 2. CAPE attenuated the histopathological effects of diazinon on lung tissue in our experimental rat model.