Most children with developmental conditions survive to adulthood. To improve adult outcomes there is a need to synthesize our existing knowledge regarding their developmental trajectories. The synthesis in this paper was guided by interactional, life course perspectives and definitions of development and disability. Evidence from 107 published articles, grey literature, and expert opinion demonstrated that there are currently more negative than positive psychosocial and mental health outcomes for youth with disabilities. Evidence is mounting that youth with disabilities experience similar trajectories to their peers without disabilities through positive, developmentally appropriate life experiences and regular opportunities with adequate supports to develop adult social roles.