Introduction Providing comprehensive, evidence-based care to perinatal people with substance use disorders (SUD) requires multi-stakeholder collaboration and alignment. The National Maternal and Child Health Workforce Development Center facilitated a system-strengthening process with the Midwest substance use in pregnancy (SUPper) club, a regional collaborative of health care providers, state public health agencies, and community-rooted organizations. Methods Facilitators led a 2 day group model building (GMB) workshop with 20 participants and two semi-structured interviews. Workshop participants were invited to complete an evaluation. Results Two primary trends were identified as priorities for change: (1) Birthing people’s perception/experience of stigma and (2) The Midwest SUPper Club’s reach and influence. Three causal loop diagrams (CLDs) were created to capture the interconnected dynamics of the Midwest perinatal SUD system: (1) the influence of stigma on maternal and infant health outcomes, (2) the role of clinic, organizational, and state policies, and (3) the impact of workforce education and evidencebased practices on care. From the CLDs, four priorities for action emerged: (1) align and promote shared mental models across stakeholders, (2) expand education and training opportunities for the perinatal SUD workforce, (3) strengthen systems infrastructure to support care navigation for patients and providers, and (4) collaboratively identify evidence-based practices that meet regional needs. All evaluation respondents reported that the workshop supported the development of a shared mental model. Discussion The GMB process strengthened collaboration and advanced strategic planning for the SUPper Club. GMB can be further utilized among diverse stakeholders across MCH systems to create shared mental models and accelerate collaborative planning efforts.