A 33-year-old woman, gravida 2, para 1, was diagnosed to have a benign mucinous cystic neoplasm of the pancreas 5 months before delivery. The tumor measured 12 cm in diameter at the time of diagnosis. The antenatal course was uneventful, and a vaginal delivery produced a normal infant. By 2 months after delivery, the tumor reached 18 cm. At surgery, a huge cyst was found to originate from the pancreas, and a distal pancreatectomy with splenectomy was performed. The cystic mass was multilocular 18 x 17 x 12 cm, 2450 g, and red to yellowish-gray. The histologic diagnosis was benign mucinous cystadenoma. The postoperative course was uneventful, and the patient remains free of recurrence at 7 months after surgery. To our knowledge, this is only the fifth reported case of pancreatic mucinous cystadenoma in association with pregnancy. This is the first reported case of a successful resection of such a tumor after delivery.