An 18-month-old girl presented with abdominal distension without abdominal pain. A cystic mass was palpable over the whole abdomen without tenderness. There were no other symptoms caused by the mass effect. Ultrasonography revealed a large unilocular, sonolucent cyst. Abdominal computed tomography (CT) showed that an enormous unilocular cyst occupied the entire abdomen. CT also demonstrated the beak sign, revealing the hepatic origin of the cyst, and the diagnosis of a simple hepatic cyst was made. The cyst was located at the periphery of segments 5 and 6. Cyst excision was planned with a minimally invasive technique. The umbilicus was opened using the three-triangular-skin-flap approach []. A purse–string suture was placed on the partially exposed cyst, and a catheter was inserted without spillage. In total, 1520 mL of yellow serous fluid was aspirated. The cystic fluid did not contain bile, with the total bilirubin level of 0.16 mg/dL and the direct bilirubin level of 0.04 mg/dL. This decompression created a large working space that enabled laparoscopic surgery. A single-port laparoscopic surgery device was applied to the umbilicus, and another 3-mm port was placed in the right lower abdomen. The cyst originated from segments 5 and 6. Using an ultrasonic coagulation incision device (Sonicision; Medtronic, Minneapolis, MN, USA), the cyst was excised en bloc together with the attached hepatic parenchyma. The operating time was 125 min, and the blood loss was 50 g. The patient was discharged on the 4th postoperative day with no complications. She was well at the 1-year follow-up. Doppler ultrasonography showed no disturbance of hepatic flow. Pathologic examination showed that most of the cyst wall was lined by a simple flattened epithelium. Immunohistochemical staining showed that the cyst epithelia were positive for cytokeratin 7, but negative for estrogen receptor.