Most autistic adults struggle with mental health problems, and traditional mental health services generally do not meet their needs. This study used qualitative methods to identify ways to improve community mental health services for autistic adults for treatment of their co-occurring psychiatric conditions. We conducted semistructured, open-ended interviews with 22 autistic adults with mental healthcare experience, 44 community mental health clinicians, and 11 community mental health agency leaders in the United States. The participants identified clinician-, client-, and systems-level barriers and facilitators to providing quality mental healthcare to autistic adults. Across all three stakeholder groups, most of the reported barriers involved clinicians' limited knowledge, lack of experience, poor competence, and low confidence working with autistic adults. All three groups also discussed the disconnect between the community mental health and developmental disabilities systems, which can result in autistic adults being turned away from services when they contact the mental health division and disclose their autism diagnosis during the intake process. Further efforts are needed to train clinicians to work more effectively with autistic adults and to increase coordination between the mental health and developmental disabilities systems.