Background: During the transition to adulthood, adolescents with long-term conditions need to take over responsibility for their care. Considering their unique developmental needs, adolescents are exposed to challenges and risks, and inadequate preparation for self-management can negatively impact long-term health outcomes. In addition, their follow-up care is transferred from a pediatric to an adult setting. Person-centered care is essential to address these critical challenges, with the STEPSTONES transition program being fit to cater these needs. Although mounting evidence for the effectiveness of transition programs, these are rarely implemented in practice. Objectives: To implement, adapt and evaluate the STEPSTONES transition program for adolescents with congenital heart disease, type-1 diabetes and, neurodevelopmental disorders in pediatric health services. Methods for implementation: A multi-faceted approach, combining stakeholder engagement, patient and public involvement, and facilitation of new practices, is employed to explore facilitators and barriers to implementation, as well as to examine how the STEPSTONES transition program can be sustained within each setting. The implementation and adaptation are conducted across six university hospitals, along with habilitation services in two healthcare regions in Sweden. Methods for evaluating implementation: The effectiveness is evaluated using a non-inferiority design where evaluation of both clinical effectiveness and implementation strategies employed will be carried out. Patient-reported outcomes will be compared to results from previous STEPSTONES RCTs, focusing on empowerment, health outcomes, and transition readiness. Participants’ and healthcare professional’s experiences of person centeredness during the transitional phase are investigated. In addition, we are exploring contextual mechanisms of impact and normalization of the transition program into standard care. Expected outcomes: The implementation of these projects will accelerate the translation of evidence into clinical practice by implementing an on-demand model of care. Furthermore, the research can provide evidence of which implementation strategies are successful in the implementation, adoption, and maintenance of person-centred transitional care.