Lemmel syndrome is a pancreaticoduodenal disease caused by compression of the mid or distal common bile duct by a periampullary diverticulum. This condition should be considered a rare complication of a duodenal diverticulum and an unusual cause of obstructive jaundice. Because of its infrequent occurrence and non-specific clinical presentation, Lemmel syndrome can mimic other conditions. We herein report the clinical and imaging findings (computed tomography, magnetic resonance imaging) of a patient who presented with intermittent abdominal pain and jaundice. Large air-filled outpouching lesions of the duodenum compressed the biliary duct, resulting in upstream biliary ductal dilatation that led to the diagnosis of Lemmel syndrome.