Achieving Thorough Transparency and Accessibility for Information Navigation on Mental Health Act of 2020 or the ATTAIN Mental Health Act This bill requires the Department of Health and Human Services (HHS) to establish and update a publicly accessible, internet-based dashboard to publicize federally funded mental health grants. The dashboard must contain, for example, program names and opening and closing dates for applications. In addition, HHS must establish a process to accept information voluntarily provided by states concerning their federally supported mental health grants for incorporation into the dashboard. In developing the dashboard, HHS must consult with appropriate federal departments and agencies and other relevant stakeholders.