The school, student and family factors underlying poor postsecondary outcomes of students with autism spectrum disorder (ASD) are not well understood. The potential impact of school [e.g., transition planning quality (TPQ)], family (e.g., parent activation), and student factors (e.g., adaptive functioning) and their interaction (e.g., parent-teacher alliance) on student outcomes were examined. Student IQ and adaptive behavior, TPQ, and alliance correlated with IEP progress, with postsecondary goal attainment generally and with student participation in training/education, specifically. However, only parent activation and student externalizing behavior correlated with employment. Families and students, rather than school personnel, were the primary persons in charge and in control of the implementation of postsecondary plans and required help across multiple coaching sessions to implement plans fully.