Backgrounds and purposeChildhood cancer survivors (CCSs) who transition through adolescence and enter young adulthood may suffer psychological, cognitive, social, fertility, and sexual issues and concerns. There is an urgent need for comprehensive intervention strategies to improve the transition of CCSs. Web-based technologies are gaining momentum as a new mechanism to provide healthcare and education for adolescents. However, previous frameworks have been limited in their effectiveness in explaining web-based interventions.This realist synthesis aims to synthesise current evidence on transition of CCSs to develop a framework for web-based interventions. The framework can foster understanding of the integrity of web-based intervention implementation chain, examine which mechanistic factors will be triggered by web-based interventions, note and examine the flows, blockages and points of contention in the implementation, to refine web-based interventions.Method and analysisA realist synthesis that adheres to the Realist and Meta-narrative Evidence Syntheses-Evolving Standard will be used. Studies will be identified through PubMed, Web of Science, EMBASE, PsycINFO, CINAHL, Ovid and Cochrane Library from the period of January 2005 to May 2023. We will also search the reference lists provided in relevant studies and reviews. Articles will be screened based on two principles: (1) Relevance: does the research address the initial programme theory? (2) Rigour: whether a particular inference drawn by the original researcher has sufficient weight to make a methodologically credible contribution to the test of the initial programme theory. No restrictions regarding the design or language of publication will be considered.Ethics and disseminationAs a review, ethical approval is not required. The results from this study will be presented at international conferences and disseminated through peer-reviewed publications. Patients and the public will be involved in the dissemination plans.