We report a case of jejunal loop obstruction by a large gallstone caused by Roux-en-Y hepaticojejunostomy-induced acute cholangitis. The patient was admitted with sepsis as well as abdominal and back pain. Abdominal computed tomography showed a dilated jejunal loop and an obstructing large mass. After his clinical condition and laboratory values improved, we performed laparotomy, which revealed a dilated jejunal loop with a palpable mass, and a gallstone was removed via enterotomy. After the disimpaction of the stone and control of the infection, his clinical condition and laboratory values continued to improve. Gallstone formation is rare after hepaticojejunostomy and to our knowledge, no other cases of acute cholangitis caused by a stone obstructing the jejunal loop have ever been reported. As with other major complications, early diagnosis and prompt initiation of surgical treatment are important to prevent any deterioration in the patient's general condition.