Fistula formation is common during the course of Crohn's disease, whereas duodenocolic fistulas are very rare. The management of internal fistulas in Crohn's disease is a complex issue. Herein, we report a case of duodenocolic fistula manifested by increasing frequency of diarrhea and loss of body weight. The fistula was diagnosed by upper gastrointestinal tract barium series, magnetic resonance enterography, and panendoscopy and was treated with a right hemicolectomy and Whipple procedure because of the simultaneous occurrence of pancreatic head tumor. Subsequent treatment with adalimumab, azathioprine, and mesalazine was prescribed for the maintenance of disease remission, and the patient was well until 18 months after the surgery.