Cystic lymphangioma is a rare malformative congenital tumor of the lymphatic vessels. It is commonly seen in children and mainly occurs in the head and cervicothoracic region. Abdominal and especially retroperitoneal involvement is rare in adults. This tumor is often asymptomatic but it can be manifested by mass effect with polymorphic symptomatology depending on the location and size. Digestive haemorrhage due to retroperitoneal cystic lymphangioma with posterior duodenopancreatic infiltration in an elderly patient is an exceptional manifestation of a benign tumor. We report a case of retro-duodenopancreatic cystic lymphangioma revealed by gastrointestinal bleeding in a 65 year-old man who was treated by tumor resection with organ preservation. The recovery was complicated by a duodenal fistula with spontaneous dry-up within 17 days, the patient left the hospital in 3 weeks.