True primary ectopic mediastinal goiter is rare and observed in less than 1% of all goiter cases. Ectopic goiter is frequently localized lingually and does not exhibit connection with the thyroid gland. Mediastinal lesions are usually located on the right side, in the anterior mediastinum, and the surgical approach in such cases is thoracotomy or sternotomy. Herein, we present a 72-year-old female patient who had undergone thyroidectomy due to thyroid papillary carcinoma 3 months before. Radioactive iodine treatment was started and scintigraphy showed nonhomogeneous pathologic activity in the anterior mediastinum. After a presumed diagnosis of anterior mediastinal mass, performing median sternotomy, multilobulated, clearly delineated, capsulated tumor without invasion into the peripheral tissues, was observed and excised. The pathology report revealed multinodular goiter. In conclusion, true primary ectopic mediastinal goiter should be considered in the differential diagnosis of mediastinal tumors, although it comprises less than 1% of them. Ectopic intrathoracic goiter should be removed surgically due to risk of malignancy and to treat compression symptoms. (The Medical Bulletin of Haseki 2010; 48: 163-5)