Aim: First, to understand the barriers to achieving effective transition and the supports required from the perspective of parents and carers, adolescents with intellectual disability and/or autism spectrum disorder and co-existing mental health disorders (often termed ‘dual disability’), and those who provide services to this group. Second, to develop an informed model of shared care to improve the transition of adolescents with dual disabilities. Method: Carers and a young adult with a dual disability were surveyed about their experience of transition care. Other key stakeholders including paediatricians, general practitioners, and policy makers were also interviewed. These data informed the model of care. Results: Paediatricians and general practitioners reported difficulties establishing working relationships to foster smooth transitions, and carers reported lacking a regular general practitioner with adequate expertise to care for people with dual disabilities. A process of shared care between paediatricians and general practitioners was developed and initiated by a dedicated transition manager, who assisted with care coordination and service linkages. Standardized clinical assessment tools were also introduced to determine patient and carer support needs. Interpretation: This study highlights the potential to improve transition outcomes for adolescents with dual disabilities and their carers through early transition planning, consistent methods of assessing patient and carer needs, and shared care.