Papillary thyroid carcinoma within the thyroglossal duct cyst is a very rare finding and its presentation is like the benign cyst. A 22 years old female patient with a midline neck mass was initially diagnosed thyroglossal duct cyst and underwent Sistrunks procedure and upon histopathologic examination she was diagnosed papillary thyroid carcinoma within the thyroglossal cyst with regional lymph node metastasis. Than she sent to radioactive iodine ablation treatment after the thyroid gland evaluation and she was followed up over eighty months free of disease. Sistrunk procedure is usually treatment of choice for the thyroglossal duct cyst, but we could rarely find malignant thyroid carcinoma within the cyst. Than we should reevaluate the thyroid gland and if there is a positive finding we should add some additional treatment like radioactive iodine ablation, total thyroidectomy, and neck dissection.