Lymphangioma is a rare, benign tumour occurring due to congenital malformation of the lymphatic channels. It occurs due to obstruction in the lymphatic channel and results in lymphangiectasia. The tumour is most commonly encountered in the head and neck regions and almost 90% are in the children below the age of 2 years. Retroperitoneal Lymphangioma in an adult is a rare clinical condition. We have presented a 41 year old female with retroperitoneal lymphangioma who came to Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh on 10 October 2017 with the non-specific complains of upper abdominal discomfort, occasional nausea, vomiting and aorexia for the last 1.5 years. She was managed surgically by exploratory laparotomy followed by de-roofing of the cyst. Histopathological examination of the cyst wall was consistent with lymphangioma.