Objective: The aim of the study was to test the effects of a generic transition-oriented patient education program on adolescents' health service participation and quality of life (QoL). Methods: We conducted a controlled trial comparing participants of 29 transition workshops with treatment as usual in 274 adolescents (16.8 mean age, SD = 1.76) diagnosed with type I diabetes (DM), cystic fibrosis (CF) or inflammatory bowel disease (IBD). A two-day transition workshop was carried out at 12 sites in Germany, focusing in standardized modules on adjustment to adult care settings, organization of future disease management, career choices and partnership. Study outcomes were health-related transition competence, self-efficacy, satisfaction with care, patient activation and QoL. Measures were assessed at baseline and six-month follow-up. Results: Repeated-measurement covariance analysis using age as a covariate showed that the transition workshop significantly affected transition competence, self-efficacy and satisfaction with school care six months post intervention. The intervention did not significantly affect patient activation and QoL. However, post-hoc analysis suggested different effects across conditions. Conclusion: The program has a positive effect on the competence of adolescents in the transition phase. Practice implications: The study demonstrates that an intervention can be effective in preparing adolescents with chronic conditions for transitions.