Adults with intellectual disabilities who experience mental illness often present with complex and multifaceted healthcare needs that require specialized assessment, treatment, and ongoing support. This presentation will define intellectual disability and review the common psychiatric, neurological, and medical comorbidities frequently encountered in adulthood. Particular attention will be given to barriers that complicate diagnosis and treatment. This talk will also review FDA-approved and commonly used pharmacologic treatments for challenging behaviors, as well as the role of behavioral and environmental interventions in comprehensive care. In addition, it will highlight important differences in the outpatient management of adults with intellectual disabilities compared with the general population.