A 54-year-old woman was admitted to our hospital because of an abnormal shadow on chest X-ray. Chest computed tomography (CT) scan and magnetic resonance imaging (MRI) demonstrated an anterior mediastinal tumor. The tumor was resected completely through a median sternotomy. The tumor was dissected successfully from the surrounding vessels in spite of the heavy adhesion to them. The blood supply of the tumor was from a branch of the brachiocephalic artery. The tumor was 9 x 8 x 3 cm in size, and was diagnosed as an aberrant mediastinal goiter since it showed no communication to the thyroid gland. An aberrant mediastinal goiter is a quite rare entity of diseases and its removal through the neck would result in uncontrolled blood loss because its blood supply usually derives from intrathoracic vessels.