Rupture of intracranial aneurysms after tissue plasminogen activator (t-PA) administration for acute ischemic stroke with an unruptured cerebral aneurysm is rare. We report a case of ruptured cerebral aneurysm after t-PA administration. A 74-year-old woman with dysarthria and left hemiparesis was admitted to our hospital, and acute lacunar infarction was found in the right corona radiata. One hour after t-PA administration, she complained of sudden headache and nausea, and her consciousness level deteriorated. Subarachnoid hemorrhage due to rupture of the anterior communicating aneurysm was confirmed and coil embolization was performed. T-PA administration for acute ischemic stroke with an unruptured cerebral aneurysm risks rupture of the cerebral aneurysm, and careful judgment is needed in each case.