Persistent sciatic artery is a congenital vascular anomaly of the arterial supply to the lower extremity. Thrombosis, distal embolization, aneurysmal dilatation, and rupture of this vessel with compression of the sciatic nerve have been recorded. Although rare in occurrence, complications of persistent sciatic artery should be included in the differential diagnosis of sciatic neuropathy. We present a case of an acute sciatic neuropathy secondary to pseudoaneurysm formation of a persistent sciatic artery. We demonstrate the diagnostic usefulness of magnetic resonance imaging.