Thoracic extramedullary hematopoiesis (EMH) is a rare disease entity that is usually associated with hematologic disorders, such as myelodysplastic or hemolytic disease. Because thoracic EMH is usually encountered as a mass during radiologic examinations, it should be differentiated from posterior mediastinal neurogenic tumors. Here, the authors report a case of EMH associated with hereditary spherocytosis. The patient underwent a complete excision by thoracoscopic surgery to differentiate it from other mediastinal tumors.