This study compares characteristics and outcomes of 70 defendants with and 1,122 without intellectual and developmental disabilities (IDD) participating in a mental health court. Demographic and clinical characteristics differed, but criminal justice or program characteristics did not. Age, race, marital status, living situation, court location, health insurance status, and likelihood of mental illness or substance abuse diagnosis differed between the two groups. When controlling for other factors, a diagnosis of IDD did not affect the odds of negative termination from the court but did reduce the odds of rearrest within 1 year of leaving the court. Some mental health courts exclude people with IDD; the study concludes inclusion is appropriate.