A non-traumatic, spontaneous hemothorax is rare. The most common causes are coagulopathy, due to anticoagulation treatment, and cancers with a metastasis to the pleural surface. Other unusual causes include thoracic endometriosis, ruptured aortic aneurysm, pulmonary arterio-venous malformation, coagulopathy, Osler-Rendeu-Weber syndrome, Ehlers-Danlos syndrome et cetera. A type 1 neurofibromatosis(Von Recklinghausen's disease) is an autosomal dominant disease that is characterized by multiple skin tumors(neurofibroma) and abnormal skin pigmentation(cafe-au-lait spots). Some are accompanied by vasculopathy, and are present with a spontaneous hemothorax. Such cases are unusual but fatal. We have recently experienced a case where a young male patient with neurofibromatosis initially presented with hypovolemic shock due to a spontaneous hemothorax. Later, aortography revealed that the cause of the hemothorax was a rupture of a pseudoaneurysm of the right internal mammary artery and as a result, an embolization was performed. Here we report this case with a review of the appropriate literature.