A 65-year-old male received coil embolization for a large internal carotid-posterior communicating artery aneurysm. Pre- and postoperative angiography at surgery demonstrated that the ipsilateral anterior choroidal artery branched from the internal carotid artery near the distal side of the aneurysm, and elevated and expanded on the aneurysmal dome, but was clearly visualized. Three days following endovascular treatment, the patient presented hemiparesis on the left side, with brain infarction in the territory of the right anterior choroidal artery despite antithrombotic therapy. The delayed brain infarction was likely caused by a reduction in anterior choroidal artery perfusion caused by mechanical compression following a postoperative increase in internal carotid-posterior communicating artery aneurysmal volume during intra-aneurysmal thrombosis. Transient volume expansion after coil embolization for intracranial aneurysms is rarely reported as a cause of brain infarction. It is important to recognize these arteries as potential postoperative complication risks, and consider the use of open surgery to avoid this risk.