Graves' disease is an autoimmune disease that affects the thyroid glands which often results in enlarged thyroid glands, and it is the most common cause of clinical hyperthyroidism especially in young patients. Radioiodine ablation is a radiation therapy in which radioactive iodine is administered to destroy or ablate thyroid cells. It is commonly used for the treatment of Graves' disease. We report on a 39-year-old male, who presented with Graves' disease, found to have pancytopenia and hypocellular bone marrow. Pancytopenia is a rare complication of thyrotoxicosis that is usually not severe and does not require supportive blood product transfusions. Our patient was treated with antithyroid medications followed by radioactive iodine ablation followed by a spontaneous recovery of pancytopenia.