BACKGROUND: Integration of HPV vaccination with other adolescent health services may be associated with favorable programme outcomes including coverage, sustainability, and equitable delivery. Interest in such integrated approaches is building. However, the empirical evidence on how an integrated approach might be used to effectively deliver HPV vaccines and other adolescent health services has not been consolidated in a manner sufficient to inform policy and programmes. METHODS: We conducted a realist synthesis review of published experiences from low- to upper-middle-income countries. Experts were invited as review commissioners, informing development and iteration of a programme theory of change (TOC). Our search strategy queried three large academic peer-review databases, grey literature, and a "snowball" of citations from key reference articles. We extracted learnings from specific real-world country experiences, exploring theoretical constructs describing the context in which an integration mechanism may deliver intended outcomes. RESULTS: Of 1961 peer-reviewed articles and 16 grey literature articles identified, 8 articles met inclusion criteria, providing data from 6 country experiences to develop an iterated TOC. There were notable gaps in evidence regarding how an integrated approach might meet unique needs of underserved populations, including out of school youth and those affected by HIV. TOC iterations yielded 9 new factors and 4 discarded factors. Notable new factors included a multisectoral cooperation mechanism, linked to the use of a large number of other mechanisms, including integration of cost-sharing, supply chain distribution, and programme monitoring. CONCLUSION: This realist synthesis is to our knowledge the first review consolidating operational evidence on how an integrated approach might be used to effectively deliver HPV vaccines and other adolescent health services. Our iterated TOC provides a framework to guide future implementation research, to ensure attribution of observed effects to an integrated approach is merited - and to inform decision-making in adolescent immunization policy and programmes.