Management of complex vascular malformation represents a challenge as it may include a wide variety of options such as embolization, laser therapy, sclerotherapy, and surgical resection but may lead to significant morbidity and is associated with high recurrence rates. In extreme and/or recurrent cases, successful use of sirolimus has been described. We report a case of large unresectable complex venous malformation treated with oral sirolimus for 24 months. Therapy was well tolerated. Patient had substantial improvement in symptoms and shrinkage of the lesion. The Medical Therapy made excision of the malformation possible and patient had a successful surgical procedure. This report provides further evidence that sirolimus should be considered as part of the armamentarium in the management of these rare conditions.