We report an unusual case of unilateral leg swelling secondary to cavernous lymphangioma (cystic hygroma), which normally affects the head and neck regions.A 25 year gentleman presented to our department with a 13-year history of gradually increasing unilateral leg swelling and recurrent infections. Investigations showed appearances consistent with cavernous lymphangioma, and partial excision of the lesion led to resolution of symptoms.The most common sites for cystic hygroma are the head and neck areas, but the extremities can be affected as demonstrated. Complete surgical excision is often difficult, and there is a tendency for recurrence. This case acts as an illustration of an uncommon yet important cause for unilateral leg swelling.