BACKGROUND: Giant and complex aneurysms are increasingly treated with the Pipeline Embolization Device (PED). However, clinical experience with the device remains preliminary. OBJECTIVE: To report the first case of a delayed migration of an intracranial PED. METHODS: A 61-year-old woman with a known large right cavernous internal carotid artery aneurysm had a 3-month history of increasing retro-orbital pain. She underwent uneventful treatment of her aneurysm with the PED. RESULTS: Five months after the procedure, the patient's pain recurred. On the routine 6-month follow-up angiography, there was proximal PED migration, with the distal end of the device projecting directly into the aneurysm and creating a jet of contrast against the aneurysm sac. The migration distance was more than 1 cm, and there was significant foreshortening of the device. A second, overlapping PED was successfully deployed within the first PED to bridge the neck of the aneurysm and redirect the flow jet away from the aneurysm sac. Complete resolution of the patient's symptoms was noted 4 weeks later. CONCLUSION: Delayed proximal migration may occur after placement of a PED. Accurate stent sizing and adequate apposition to the vessel wall may minimize the occurrence of this undesirable phenomenon. If there is any concern regarding the position of the PED, early imaging follow-up may be indicated.