A 65 year-old female presented with diarrhea, body weight loss, malnutrition, elevated serum carcinoembryonic antigen (CEA) and electrolyte disturbances. A series of examinations showed colon cancer with a malignant duodenocolic fistula. Patient received extended right hemicolectomy with wide local excision of the duodenum (en bloc resection of the tumor). Recovery was smooth without local recurrence or metastasis after a six-month follow-up. Wide en bloc resection provides the only hope of cure in such cases. Treatment with extended right hemicolectomy with Whipple's procedure, or extended right hemicolectomy with extended local wide excision of duodenum, should be chosen, depending upon the extent of tumor invasion.