Chordoma is an uncommon malignant bone tumor that originates from the remnants of the embryonic notochord. In most of the reported cases, chordomas occur at the skull base or in the sacrococcygeal spine but rarely in the thoracic spine. In this report, we describe a case of a large thoracic chordoma with posterior mediastinal extension in a 25-year-old woman who presented with left-hand anhydrosis. The imaging studies, pathology findings, and recent advances in treatment are discussed.