Objectives Multiple osteochondromas (MO) is a rare hereditary disease characterised by numerous benign bone tumours. Its chronic aspect requires a well-organised transition from paediatric care to adult care; however, little is known on organising this care specific for patients with MO. This study aims to gain insight on this topic. Design Convergent mixed-method study. Setting This study was conducted at the orthopaedic and paediatrics department of an MO-expertise centre in the Netherlands. Participants 12 patients, 10 parents and 10 healthcare professionals were interviewed. An additional survey was completed by 2 young adults. Primary and secondary outcomes The (1) themes on transition, identified through template analysis and (2) transfer experience and satisfaction assessed by an 18-item On Your Own Feet-Transfer Experience Scale (OYOF-TES, range: 18-90) and by Numeric Rating Scale (NRS, range: 1-10). Results The following three key themes were identified in the qualitative analysis: (1) patient and parent in the lead can be encouraged by self-management tools, (2) successful transfers need interprofessional collaboration and communication and (3) how can we prepare patients for the transitional process? Stakeholders' insights to improve transition were listed and divided into these three themes. Several important aspects were underlined, particularly within the first theme; speaking-up was difficult for patients especially when parents were not directly involved. Moreover, the high psychological impact of the disease requires coaching of self-management and psychological counselling to facilitate stakeholders in their changing roles. Twenty patients completed the quantitative survey. Mean satisfaction score with the transfer process was poor, which was assessed with the NRS (mean=5.7±2.1; range: 1-9) and the OYOF-TES (mean=56.3±14.2; range: 32-85). The OYOF-TES only showed a negative correlation (R 2 =0.25; p=0.026) with the number of surgical interventions in the past. Conclusion Overall, the transfer process was found unsatisfactory. Improvement can be achieved by supporting and guiding the patients to be in the lead of their care. Moreover, preparation for transfer and a multidisciplinary approach may enhance successful transition.