Gastrojejunocolic fistula, a rare but serious complication of gastrojejunostomy often results from inadequate resection or incomplete vagotomy during gastric surgery. The most common symptoms include feculent vomiting, chronic diarrhea, and weight loss, and surgical repair is the definitive treatment for this condition. A 51-year-old man presented to our hospital with upper abdominal pain and chronic diarrhea. He had a history of gastric surgery for gastric cancer, 20 years prior at another hospital. Upper endoscopy and abdominal computed tomography confirmed diagnosis of a gastrojejunocolic fistula. In this case report, we present the clinical features and diagnostic approaches for gastrojejunocolic fistulas.