Conventional treatments for Graves' disease include thionamides, radioactive iodine therapy (RAI), and thyroidectomy. Occasionally, patients may develop resistance to thionamides and may require additional treatment. We present the case of an adolescent girl with thionamide-resistant Graves' disease who was successfully treated with lithium and subsequent RAI after stabilizing her thyroid hormone levels. Following RAI, the patient developed hypothyroidism, and thyroxine replacement therapy was initiated. This case highlights the potential of lithium as a safe and effective alternative for controlling hyperthyroidism in Graves' disease and its role in preparing patients for more definitive treatment.