We herein present an exceedingly rare case of intrathoracic ganglioneuroma that was surgically resected in an elderly patient over 70 years of age. A 74-year-old woman was asymptomatic, but a computed tomography (CT) scan of the thorax indicated the presence of a posterior mediastinal mass paravertebrally. A thoracotomy was thus performed under a strongly suggested diagnosis of a neurogenic tumor because of the appearance and position of the mass on the chest CT and magnetic resonance imaging findings, and measuring 6.9 x 5.8 x 1.6 cm. Not only tumors originating from the nerve sheath, but also neurogenic tumors occurring in young patients such as ganglioneuroma, should be included in the different diagnosis of posterior mediastinal tumor occurring in elderly patients.