An 85-year-old man presented to our hospital with hemoptysis and subcutaneous masses. Unenhanced computed tomography (CT) scan revealed multiple tumors of the chest wall, vertebrae, and ilium. We performed a needle biopsy of a subcutaneous tumor on the left lower back, and a diagnosis of angiosarcoma was made. CT scan also revealed multiple small nodules together with ground-glass opacities bilaterally in the peripheral lung fields. Bronchoscopy with bronchoalveolar lavage (BAL) was performed with progressively bloody BAL returns. Bronchial brush cytology showed hemosiderin-laden macrophages and atypical spindle-shaped cells, corresponding to metastatic angiosarcoma. We concluded that metastatic lung angiosarcoma was the cause of the diffuse alveolar hemorrhage (DAH). Although angiosarcoma is an extremely rare malignant neoplasm, it frequently leads to DAH originating from pulmonary lesions and should be included in a differential diagnosis of DAH.