To design PARTNER-MH, a peer-led, patient navigation program for implementation in Veterans Health Administration (VHA) mental health care settings, we conducted a pre-implementation evaluation during intervention development to assess stakeholders' views of the intervention and to explore implementation factors critical to its future adoption. This is a convergent mixed-methods study that involved qualitative semi-structured interviews and survey data. Data collection was guided by the Consolidated Framework for Implementation Research (CFIR). We interviewed and administered the surveys to 23 peers and 10 supervisors from 12 midwestern VHA facilities. We used deductive and inductive approaches to analyze the qualitative data. We also conducted descriptive analysis and Fisher Exact Test to compare peers and supervisors' survey responses. We triangulated findings to refine the intervention. Overall, participants viewed PARTNER-MH favorably. However, they saw the intervention's focus on minority Veterans and social determinants of health framework as potential barriers, believing this could negatively affect the packaging of the intervention, complicate its delivery process, and impact its adoption. They also viewed clinic structures, available resources, and learning climate as potential barriers. Peers and supervisors' selections and discussions of CFIR items were similar. Our findings informed PARTNER-MH development and helped identify factors that could impact its implementation. This project is responsive to the increasing recognition of the need to incorporate implementation science in healthcare disparities research. Understanding the resistance to the intervention's focus on minority Veterans and the potential barriers presented by contextual factors positions us to adjust the intervention prior to testing, in an effort to maximize implementation success.