This document introduces the ACMHI Mentally Healthy Campus Maturity Model, which was created to help post-secondary institutions collaboratively improve mental health and wellness on campuses. The maturity model visualizes capabilities and development in three stages with five levels to focus efforts on complex systemic challenges. It can be used by individual institutions to assess themselves or collectively to identify gaps and overlaps between organizations. The model addresses four dimensions in increasing detail levels from basic to advanced. The goal is to facilitate shared understanding and conversations between institutions to inform decisions and progress towards the shared vision of mentally healthy campuses.