Information on admission to psychiatric inpatient units is lacking from the literature on contemporary services for people with intellectual disability and mental health needs. Here we report on predictors of admission for a cohort of 752 adults from this population living in community settings; 83 were admitted. We also report on two subsamples of this cohort for whom different psychometric measures concerned with psychiatric symptoms and behavior had been completed. Schizophrenia spectrum disorders and mild intellectual disabilities independently predicted admission for the total cohort. The presence of symptoms associated with psychosis and the presence of physical aggression predicted admission in the subsamples.