This study estimated patterns and trends in all-cause (any reason, including psychiatry related) and psychiatric emergency department (ED) utilization among Medicare beneficiaries under 65 who were residing in community settings (i.e., noninstitutionalized or in their own homes). Medicare beneficiaries under the age of 65 enrolled in Medicare for Social Security Disability Insurance (SSDI) due to permanent physical or mental disabilities are a population with poor health conditions and high utilization of health services; however, this vulnerable population has received limited attention from researchers and policymakers compared to the Medicare beneficiaries 65 years and older. Data from the 2002–2009 Medicare Current Beneficiary Survey (MCBS) with linked Medicare administrative claims data were used to select a total of 4,864 Medicare beneficiaries under the age of 65 with a total of 10,384 person-years (weighted n = 30,086,846 person-years). We found that trends in all-cause and psychiatric ED utilization among the young and disabled Medicare beneficiaries remained stable, but trends in the proportion of all-cause ED visits that were psychiatric related increased, and trends in the proportion of psychiatric ED visits resulting in a psychiatric inpatient stay decreased over time. Factors associated with a higher likelihood of psychiatric ED utilization included younger age, residence in the Northeast region, lower education level, Medicare–Medicaid dual eligibility, use of psychotropic medication, and greater number of chronic and psychiatric conditions. These findings highlight the need for policies, programs, and system interventions designed to reduce future psychiatric ED events and improve the access and quality of community mental health services for the community-dwelling, young, and disabled Medicare population.