We herein describe a case involving spontaneous rerupture of a nonparasitic liver cyst successfully treated with cyst fenestration and an omental flap. A 59-year-old Japanese woman was transferred to our hospital for evaluation of acute abdominal pain. She had a history of conservative treatment with antibiotics for spontaneous rupture of a liver cyst 1 month previously. On arrival, she exhibited abdominal tenderness and muscular defense. Enhanced computed tomography showed ascites and a large ruptured hepatic cyst (diameter of 10 cm). We diagnosed rerupture of a liver cyst and performed laparotomy for cyst fenestration and intraperitoneal drainage. During the operation, we found the perforation site on the ventral side of the cyst and brown, muddled ascitic fluid. Cholangiography showed no bile leakage on the inner wall. Pathological investigation revealed no evidence of malignancy. The patient recovered without any adverse events and was discharged on postoperative day 8. No recurrences or complications occurred for 2 years.