The authors report a 12-year-old girl who presented with a 2-year progressive painless thoracic scoliosis. Her previous development had been normal with no significant past history of illness. MRI revealed a thoracic ganglioneuroma, which was confirmed by surgical pathology. Ganglioneuroma might cause progressive spinal deformity mimicking adolescent idiopathic scoliosis. A careful preoperative survey is mandatory for patients diagnosed with scoliosis with a rigid or rapidly progressive curve. The authors recommend a combination of neurosurgery and orthopedic spine surgery to treat this condition.