<p>Lymphangiomas are uncommon congenital benign tumors of the lymphatic system. They are typically diagnosed at birth and develop during the first years of life. The tongue is the most commonly affected structure in the oral cavity. Lymphangioma circumscriptum of the tongue is a common cause of macroglossia in children, and this macroglossia can lead to complications such as exclusive nasal breathing, airway obstructions, impaired oral feeding, esthetic disfigurement, and difficulties in mastication, swallowing, and speech. This report discusses the successful treatment of lymphangioma circumscriptum of the tongue with sirolimus, an immunosuppressant drug. The extent of the lesion made traditional surgical management impossible without excessive morbidity, so the patient was managed medically. This case report was unique due to its entirely nonsurgical treatment approach. The patient completed a 17-month course of sirolimus monotherapy with response to treatment monitored using T2 MRI. There was excellent response to treatment, full resolution of symptoms, and no treatment-related toxicity.</p>