We report a case of Hughes-Stovin syndrome (HSS) associated with hyperhomocysteinemia. A 24-year-old man who has no clinical features suggestive of Behcet's disease was admitted for hemoptysis and dyspnea. Radiological and laboratory evaluation revealed multifocal pulmonary artery aneurysms involving bilateral segmental pulmonary artery, thrombi in right atrium and ventricle, and hyperhomocysteinemia. Accordingly, HSS associated with hyperhomocysteinemia was diagnosed, and the clinical and radiological improvement was achieved after treatment with prednisolone, warfarin, and folic acid.