Drawing on the principle of subsidiarity, this article develops a framework for allocating medical decision-making authority in the absence of capacity to consent and argues that decisional authority in paediatric transgender healthcare should generally lie in the patient. Regardless of patients’ capacity, there is usually nobody better positioned to make medical decisions that go to the heart of a patient’s identity than the patients themselves. Under the principle of subsidiarity, decisional authority should only be held by a higher level decision-maker, such as parents or judges, if lower level decision-makers are incapable of satisfactorily addressing the issue even with support and the higher level decision-maker is better positioned to satisfactorily address the issue than all lower level decision-makers. Because gender uniquely pertains to personal identity and self-realisation, parents and judges are rarely better positioned to make complex medical decisions. Instead of taking away trans youth’s authority over their healthcare decisions, we should focus on supporting their ability to take the best possible decision for themselves.