In acute pancreatitis, colonic complications such as mechanical obstruction, ischemic necrosis, hemorrhage, and fistula are rare but their outcomes are fatal. It is known that colonic obstruction in acute pancreatitis is more likely found in splenic flexure and transverse colon caused by severe inflammation of body and tail of pancreas leading to pressure necrosis. A 43-year-old man presented with abdominal distension lasting for 2 weeks. The patient had been admitted to our institution 6 weeks prior to the current admission, and the abdominal CT scan performed during the first admission revealed the pancreatic enlargement with peri-pancreatic fatty infiltration and fluid collection. At that time he was diagnosed as acute pancreatitis. The conservative management resulted in clinical improvement so that the patient was discharged. Upon the second admission, abdominal CT scan revealed multiple pseudocysts in the tail portion of pancreas with concominant wall thickening and narrowing of the proximal descending colon, and a dilatation of the bowel proximal to the splenic flexure. An obstruction of the descending colon as a complication of acute pancreatitis was suspected and the patient underwent left hemicolectomy. Abdominal distension was relieved after the operation and he was discharged on the 15th hospital days.