We report a case of a 44-year-old woman with metastatic brain tumors who suffered peri-tumoral hemorrhage soon after stereotactic radiosurgery (SRS). She had been suffering from breast cancer with multiple systemic metastasis. She started to have headache, nausea, dizziness and speech disturbance 1 month before admission. There was no bleeding tendency in the hematological examination and the patient was normotensive. Neurological examination disclosed headache and slightly aphasia. Magnetic resonance imaging showed a large round mass lesion in the left temporal lobe. It was a well-demarcated, highly enhanced mass, 45 mm in diameter. SRS was performed on four lesions in a single session (Main mass: maximum dose was 30 Gy in the center and 20 Gy in the margin of the tumor. Others: maximum 25 Gy margin 20 Gy). After radiosurgery, she had severe headache, nausea and vomiting and showed progression of aphasia. CT scan revealed a peritumoral hemorrhage. Conservative therapy was undertaken and the patient's symptoms improved. After 7 days, she was discharged, able to walk. The patient died of extensive distant metastasis 5 months after SRS. Acute transient swelling following conventional radiotherapy is a well-documented phenomenon. However, the present case indicates that such an occurrence is also possible in SRS. We have hypothesized that acute reactions such as brain swelling occur due to breakdown of the fragile vessels of the tumor or surrounding tissue.