Pseudoaneurysms of the extracranial carotid arteries are rarely seen following irradiation for cancers of the head and neck. We present a patient with a pseudoaneurysm of the common carotid artery following a radical neck dissection and irradiation for thyroid carcinoma 20 years earlier. Following oesophagoscopical examination, a pseudoaneurysm of the right common carotid artery ruptured into the piriform sinus. The common carotid artery was embolized with multiple coils and the bleeding was halted. The relationship between the carotid artery aneurysm and irradiation, and the treatment of carotid artery aneurysm, is discussed.