A 73-year-old woman was admitted to our hospital with a sudden onset of upper abdomimal pain and nausea. Small intestinal volvulus was diagnosed based on the presence of a "whirl sign" on contrast-enhanced abdominal CT and emergency surgery was performed. The small intestine had rotated 720° clockwise. We rotated the small intestine back to the correct position. The small intestine showed no necrosid. A mass 5 cm in diameter was found to originate from the jejunal wall, 30 cm distal from the ligament of Treitz. She underwent resection of the jejunal mass. The cecum was liberated from the retroperitoneum. This was a rare case of small intestinal volvulus with free cecum and duplication.