A group of 12 domestic pigeons (Columba livia domestica) was treated for capillariasis by use of fenbendazole at 30 mg/kg orally once daily for 5 d. After treatment, 8 of the 12 pigeons exhibited signs of anorexia, lethargy, and dehydration; these birds died within 2 d after the onset of clinical signs. A total of 6 birds were necropsied, and all had unremarkable gross findings. Microscopic examination of tissues revealed acute hemorrhagic enteritis, diffuse lymphoplasmacytic enteritis, small intestinal crypt necrosis, periportal lymphoplasmacytic hepatitis, bile duct hyperplasia, and renal tubular necrosis. Erythrocytes in blood samples collected from surviving birds demonstrated polychromasia compatible with a regenerative anemia. The clinical and histopathologic findings in these pigeons were consistent with recent reports of fenbendazole toxicity in domestic pigeons and other columbiform birds.