Primary craniosynostosis is a congenital craniofacial disorder in which cranial sutures prematurely close. Iatrogenic secondary stenosis is abnormal cranial suture closure caused by surgical manipulation of the suture. In contrast, idiopathic secondary stenosis develops in a suture that did not undergo surgical manipulation. The objective of this systematic review was to consolidate and characterize the incidence, classification, and management of idiopathic secondary stenosis in the literature./r/nLiterature from PubMed, Web Of Science, and EMBASE from 1970 to March 2022 was reviewed. The following information was extracted for individual patients: incidence of idiopathic secondary stenosis, index primary craniosynostosis, primary surgical correction, presenting signs of secondary stenosis, management, and further complications./r/nSeventeen articles detailing 1181 patients were included. Ninety-one developed idiopathic secondary stenosis (7.7%). Only 3 of these patients were syndromic. The most common index craniosynostosis was sagittal synostosis (83.5%). The most common suture undergoing idiopathic secondary stenosis was the coronal suture (91.2%). Patients presented at a median age of 24 months. The most common presenting sign was a radiologic finding (85.7%), although some patients presented with headache or head deformity. Only 2 patients, both syndromic, had complications following surgical correction of secondary stenosis./r/nIdiopathic secondary stenosis is a rare, long-term complication following index surgical repair of craniosynostosis. It can occur following any surgical technique. It most commonly affects the coronal suture but can affect any of the sutures, including pansynostosis. Surgical correction is curative in nonsyndromic patients.