A posterior mediastinal mass was found incidentally in a 70-year-old woman during a work-up for an early breast cancer. Computed tomography of the chest showed a well-circumscribed mass near the left subclavian artery and proximal descending aorta. A left video assisted thorascopic excision of the posterior mediastinal mass was performed. Pathologic examination showed it to be a chondromatous hamartoma, representing a very unusual location for this type of tumor.