Transitional age youth (TAY) are in a discrete developmental stage, different from both adolescents and mature adults. Serious mental illness can result in their delayed psychosocial development and morbidity. Systemic, provider, and individual barriers result in poor access to care for these youth, potentially impeding their transition to mature adulthood. Current strategies for TAY treatment include patient centered care, vocational and educational support, and shared decision making. There is a paucity of evidence-based practices to effectively treat this population or provide practice guidelines. The research required to do so should be a priority.