The aim of the present study was to investigate for the first time adverse effect of fenamiphos on the eart- hworm, Eisenia fetida. Earthworms were exposed to different concentrations of fenamiphos (5, 10 and 20 mg/kg). After 96 h, earthworms were euthanized and fixed. Histological alterations in earthworm’s body wall (epidermis, circular and longitudinal muscles), chloragogenous tissue and intestinal epithelium were asses- sed. Histopathological changes were more prominent in medium (10 mg/kg) and high-concentration (20 mg/ kg) groups than in the low-concentration (5 mg/kg) group. Degeneration in the intestine and integumentary system, as our results indicated after exposure to fenamiphos, are likely to interfere with the correct functio- ning of the intestine and integumentary system may affect earthworm survival.