Adults with intellectual and developmental disabilities (IDD) frequently become frail earlier than the general population, resulting in higher care needs. This population is at risk for institutionalization, or re-institutionalization, into long-term care (LTC). Using a retrospective cohort design to follow 3,034 individuals (18-99 years) living in Ontario, Canada, and assessed with the Resident Assessment Instrument–Home Care, individuals were characterized with a frailty index (FI) for persons with IDD. Survival analyses determined differences in rates of admission to LTC and survival in the community. Frail individuals had greater rates of admission than non-frail individuals, adjusted HR = 2.19, 95% CI [1.81, 2.64]. The FI predicts institutionalization.