Angiosarcoma is a rare malignant tumor occurring in less than 2% of soft tissue sarcomas. Angiosarcoma involving the kidney usually represents metastasis from skin or visceral primary lesions, while angiosarcoma primarily occurring in the kidney is a very rare neoplasm. In the English literature, from 1942 to the present, only 19 cases of primary kidney angiosarcoma have been reported. A case of primary renal angiosarcoma presenting as a large kidney mass and flank pain occurring after traumatism is reported. The present case represents further evidence of a rare malignancy.