Congenital lymphangioma circumscriptum (LC) of the vulva is a rare disorder with unknown etiology. Treatment options include ablative approaches such as laser therapy, sclerotherapy, and surgery. Radiotherapy has been shown to be effective in the management of congenital lymphangioma especially in the thoracic and abdominal lesions. In this report, we describe a patient with persistent vulvar LC despite sclerosing therapy and several surgical excisions. She was treated with a course of external radiotherapy and showed a dramatic objective response with relief of all symptoms.