Background Transitions from paediatric to adult health-care services cause problems worldwide, particularly for young people with long-term conditions. Sickle cell disorder brings particular challenges needing urgent action. Objectives Understand health-care transitions of young people with sickle cell disorder and how these interact with broader transitions to adulthood to improve services and support. Methods We used a longitudinal design in two English cities. Data collection included 80 qualitative interviews with young people (aged 13–21 years) with sickle cell disorder. We conducted 27 one-off interviews and 53 repeat interviews (i.e. interviews conducted two or three times over 18 months) with 48 participants (30 females and 18 males). We additionally interviewed 10 sickle cell disease specialist health-care providers. We used an inductive approach to analysis and co-produced the study with patients and carers. Results Key challenges relate to young people’s voices being ignored. Participants reported that their knowledge of sickle cell disorder and their own needs are disregarded in hospital settings, in school and by peers. Outside specialist services, health-care staff refuse to recognise patient expertise, reducing patients’ say in decisions about their own care, particularly during unplanned care in accident and emergency departments and on general hospital wards. Participants told us that in transitioning to adult care they came to realise that sickle cell disorder is poorly understood by non-specialist health-care providers. As a result, participants said that they lack trust in staff’s ability to treat them correctly and that they try to avoid hospital. Participants reported that they try to manage painful episodes at home, knowing that this is risky. Participants described engaging in social silencing (i.e. reluctance to talk about and disclose their condition for fear that others will not listen or will not understand) outside hospital; for instance, they would avoid mentioning cell sickle disorder to explain fatigue. Their self-management tactics include internalising their illness experiences, for instance by concealing pain to protect others from worrying. Participants find that working to stay healthy is difficult to reconcile with developing identities to meet adult life goals. Participants have to engage in relentless self-disciplining when trying to achieve educational goals, yet working hard is incompatible with being a ‘good adult patient’ because it can be risky for health. Participants reported that they struggle to reconcile these conflicting demands. Limitations Our findings are derived from interviews with a group of young people in England and reflect what they told us (influenced by how they perceived us). We do not claim to represent all young people with sickle cell disorder. Conclusions Our findings reveal poor care for young people with sickle cell disorder outside specialist services. To improve this, it is vital to engage with young people as experts in their own condition, recognise the legitimacy of their voices and train non-specialist hospital staff in sickle cell disorder care. Young people must be supported both in and outside health-care settings to develop identities that can help them to achieve life goals. Future work Future work should include research into the understanding and perceptions of sickle cell disease among non-specialist health-care staff to inform future training. Whole-school interventions should be developed and evaluated to increase sickle cell disorder awareness. Funding This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 8, No. 44. See the NIHR Journals Library website for further project information.