Objective: The implementation of evidence-based treatments (EBTs) to address posttraumatic stress disorder (PTSD) is a public health priority. Successful EBT implementation requires effective collaboration between multiple stakeholder groups, including hospital leaders, providers, and patients, to build buy-in for this effort. Method: We describe our implementation science approach to meaningful stakeholder engagement, as part of a hybrid type I effectiveness-implementation trial of Skills Training in Affective and Interpersonal Regulation for PTSD treatment in primary care (STAIR-PC) at a large safety net hospital. We used primary care and patient community advisory boards (CABs) to interpret key informant interviews and identify strategies to adapt the intervention to ensure fit with the primary care setting. We documented our stakeholder engagement methodology through comprehensive field notes and minutes from CAB meetings, detailing the focus of meetings, suggestions for intervention and delivery adaptations, decision-making processes, and how disagreements about adaptations between stakeholders were resolved. To support replicability, we specify and operationalize implementation strategies to be used across each implementation phase of the trial. Results: Key strategies involved a) ensuring that research questions are relevant to both patients and clinical providers; b) tailoring interventions that are flexible and adaptable to the needs of the local setting; c) continuous engagement of patients and providers throughout the implementation process; and d) building mutual respect, trust, and credibility between the research team, various provider groups, and patients. Conclusions: Our approach to engaging stakeholders informed an implementation blueprint to guide implementation of EBTs for PTSD in safety net hospital primary care clinics. (PsycInfo Database Record (c) 2022 APA, all rights reserved).