Background: Teenage and young adult (TYA) survivors of childhood brain tumours and their family caregivers can experience many late effects of treatment that can hamper the transition to living independent lives. Yet, their long-term supportive care needs are largely unknown. We investigated the supportive care needs of TYA survivors and their caregivers and explored the role and perceived use of support. Methods: Face-to-face semi-structured interviews were conducted with survivors aged 16–30 (n = 11) who were ≥ 5 years after diagnosis and caregivers (n = 11). Interviews were recorded and transcriptions thematically analysed. Results: Four themes emerged: (1) preferences for support and support services (unmet needs). Concerns regarding mental health, employment and financial uncertainty, the desire to live independently, and lack of support were emphasised. (2) Decline in support. Caregivers noted a drop-off in support available when transitioning to adult services. (3) Reasons for not obtaining adequate support. Several barriers to accessing support were raised, including distance and aging out of services. (4) The role of long-term hospital-based follow-up care. Participants highlighted the importance of, and reassurance from, long-term follow-up care but noted a more all-inclusive approach is required. Conclusions: Even many years after diagnosis, TYA childhood brain tumour survivors and their caregivers continue to have unmet supportive care needs. Both TYA survivors and their caregivers can benefit from support to meet their unique needs and improve long-term quality of life. Understanding unmet needs and recognising what services are required due to the late effects of treatment is critical to improving long-term quality of survival.