Neurofibromatosis type 1 (NF-1) is a genetically inherited disorder that may cause skin abnormalities and tumors that form on nerve tissues. These tumors can be small or large and can occur anywhere in the body, including the brain, spinal cord, or other peripheral nerves. Retroperitoneal lymphangiomas are very rare benign malformations of the lymphatic system. About 95% lymphangiomas occur in the skin and the subcutaneous tissues of the head, neck and axillary region and the remaining 5% appear in other parts of the body such as lungs, pleura, pericardium, liver, gallbladder, kidney, and the mesentery. Herein, we report the case of a giant retroperitoneal lymphangioma in a patient with NF-1 with a review of the literature.