OBJECTIVE: Individuals with intellectual and developmental disabilities disproportionately use emergency psychiatric services compared with their neurotypical peers, suggesting that such individuals and their supports are at increased risk for crisis events. This prospective study examined the timing, outcomes, and predictors of mental health crises for this population. METHODS: The data came from Systemic, Therapeutic, Assessment, Resources, and Treatment (START), a national model that provides mental health crisis services for those with intellectual and developmental disabilities in the United States. The study included 1,188 individuals from four U.S. regions enrolled between 2018 and 2019. The outcome was urgent crisis contacts with the START program. Baseline and clinical predictors were examined with multivariate regression analyses. RESULTS: More than a quarter had at least one crisis contact, and 9% had three or more. Contacts increased within the initial 3 months of START enrollment, followed by a steep drop-off thereafter; few contacts happened after 1 year. Almost 45% of the contacts occurred after hours, and 30% involved police. Clinical factors predicted crisis contact most robustly, followed by lack of occupational supports. After START crisis intervention, 73% of individuals remained in their primary setting. CONCLUSIONS: For individuals with intellectual and developmental disabilities and mental health needs, crisis stabilization resources are needed, including after hours. Results clearly identify times and risk factors for mental health crisis contacts, including frequent involvement with emergency responders. Importantly, gainful employment conveyed benefits for community stabilization. Findings may be leveraged to develop effective mental health crisis intervention services and supports for this underserved group.