A ruptured blisterlike aneurysm of the supraclinoid ICA rarely occurs. Nevertheless, it is recognized as a dangerous lesion because of the high risk of intraoperative bleeding associated with this lesion's wide fragile neck. There has been only one report of a blisterlike aneurysm treated by endosaccular packing after surgical wrapping. The authors describe the case of a ruptured blisterlike aneurysm with a pseudoaneurysm cavity, which was treated by coil embolization. This 63-year-old woman suffered a subarachnoid hemorrhage (SAH). Three cerebral aneurysms were identified on cerebral angiograms. A large saccular aneurysm at the ophthalmic portion of the right ICA was embolized with Guglielmi Detachable Coils (GDCs). Two small hemipherically shaped aneurysms on the C-2 and C-3 portions of the left ICA were observed conservatively. Thirteen days later, recurrent SAH was identified on computerized tomography scans. Angiography demonstrated the formation of a pseudoaneurysm from the aneurysm on the C-2 portion of the left ICA. Endosaccular embolization with GDCs was performed 40 days after admission. Disappearance of the pseudoaneurysm cavity and residual dome filling was seen immediately after the procedure. Follow-up angiography performed 9 months after embolization demonstrated complete obliteration of the aneurysm. This case illustrates that when treatment options for a blisterlike aneurysm with a pseudoaneurysm are unsuitable during the acute phase, coil embolization can be applied following progression of the lesion into a saccular aneurysm during the chronic stage.