Nodular goiter is a common disease in Taiwan, and substernal or intrathoracic goiters are not infrequent. However, intrathoracic goiters are mainly of the secondary type and primary intrathoracic goiters are rarely seen. We report a 55-year-old woman who was incidentally found to have an ectopic goiter located in the anterior upper mediastinum with the initial presenting symptom of productive cough. Imaging studies including chest X-ray and computed tomography identified the lesion, and 131I-uptake scan showed weak uptake in the thorax. Surgical removal via thoracotomy was performed and the diagnosis was confirmed by pathology. A primary intrathoracic goiter, although rare, should also be considered in the differential diagnosis of mediastinal tumor.