Endoscopic endonasal surgery on a 36-year-old man was complicated by perforation of the right internal carotid artery. The immediate, substantial haemorrhage was controlled by packing the sphenoid sinus. Intra-arterial angiography of the right internal carotid artery showed small irregularities proximal to the ophthalmic artery. A follow-up examination two weeks later documented a large pseudoaneurysm in the initially irregular arterial segment, which was successfully treated by endovascular coiling. This case report illustrates the need for angiographic follow-up examinations following traumatic intracranial vessel injury in order to identify late pseudoaneurysm development.