One adult (13-yr-old) and two young (3–4-yr-old) male dromedary camels (Camelus dromedarius) from the Seoul Zoo displayed anorexia and chronic diarrhea for 2 wk. Direct fecal smear examination revealed Trichuris spp. infection. After confirmation of the infection, fenbendazole was orally administered as a suspension; this was repeated two times at 3-wk intervals. A high initial dose (20 mg/kg) was followed by administration at the recommended dose (10 mg/kg). Starting on the day following the first treatment, a large number of adult whipworms were discharged with the feces over a 3-day period. Two young male dromedary camels gradually recovered. However, the adult male dromedary camel developed continuous bloody mucoid diarrhea and died 2 days after treatment. Postmortem examination revealed that numerous whipworms were attached to the mucosa throughout the large intestine.