The patient was a 74 year-old woman. She came to the hospital with the chief complaint of vomiting, difficulty walking, and disorientation. The MRI study showed increased FLAIR and DWI signals in the bilateral medial thalamus. Abdominal enhanced CT scan showed a 2.4 cm tumor in the jejunum. And ileus due to small intestinal tumor was observed. She diagnosed Wernicke's encephalopathy associated with gastrointestinal transit disorder. Vitamin B1 300 mg/day for 3 days was started, and eye movements and disorientation improved on the day following the start of administration. On the 10th day after admission, partial resection of the small intestine was performed for a small intestinal tumor. She was diagnosed as small intestinal cancer. She was transferred to the hospital on the 20th postoperative day.