Radiation necrosis with massive hemorrhage is a rare complication of radiotherapy. We report the case of a male patient who had undergone radiotherapy therapy 18 years earlier and presently underwent gamma knife radiosurgery for a metastatic brain tumor in his right occipital lobe. The patient showed aberrant behavior with left homonymous hemianopsia and a gradual deterioration of cognitive function after radiotherapy. A CT scan showed the presence of an intracerebral hematoma over the right occipital lobe with mass effect, and small spotty enhancements on the lesion when enhanced on gadolinium contrast-enhanced MRI. Intraoperative findings revealed necrosis of the occipital surface and a hematoma in the occipital lobe. Pathological findings showed damage to the walls of the sinusoidal capillaries and vitreous degeneration of the inner membrane with a spongiform hemangioma. After surgery, the cerebral edema resolved, and the patient's clinical symptoms improved. The cause of the radiation necrosis and bleeding in this patient was assumed to be due to the breakdown of the congested walls of the sinusoidal capillary vessels.