A 72-year-old female presented with episodes of epistaxis. Neuroimaging demonstrated a large prolactinoma totally enclosing a large intracavernous aneurysm of the internal carotid artery. Adjacent bony structures were eroded and destroyed by tumor invasion and extension. Rupture of the intratumoral aneurysm caused fatal epistaxis rather than subarachnoid hemorrhage before surgery. Intratumoral aneurysm is rare and epistaxis caused by rupture of it is extremely rare. Lack of bony protection apparently have contributed to the aneurysmal growth and rupture.