The patient was a 79-year-old man who visited our hospital with the chief complaint of persistent watery diarrhea. This symptom and his general condition aggravated during the planning of colonoscopy, and he was admitted to the intensive care unit. Large-volume fluid replacement, vasopressor administration, and artificial respiration management were performed;however, circulatory dynamics did not improve. Based on his medication history, he was diagnosed with distigmine bromide-induced cholinergic crisis. Atropine sulfate was administered, and his symptoms reduced. On colonoscopy, there were no abnormal findings other than adenoma, and the patient was discharged while in remission.