Radioactive iodine (RAI) therapy plays an important role in the management of thyroid malignancies. Leukemia is a very rare complication of radioactive therapy. There are very few case reports with doses below 100 mCi causing leukemia. We report a case of papillary carcinoma of the thyroid treated with 80 mCi RAI who later developed acute myeloid leukemia. Thus, all patients with thyroid carcinoma treated with RAI should undergo periodic hematological examinations irrespective of RAI dose.