Evidence synthesis is key in promoting evidence-based health care, but it is resource-intense. Methods are needed to identify and prioritize evidence synthesis needs within health care systems. We describe a collaboration between an agency charged with facilitating the implementation of evidence-based research and practices across the Military Health System and a research center specializing in evidence synthesis. Methods: Scoping searches targeted 15 sources, including the Veterans Affairs/Department of Defense Guidelines and National Defense Authorization Acts. We screened for evidence gaps in psychological health management approaches relevant to the target population. We translated gaps into potential topics for evidence maps and/or systematic reviews. Gaps amenable to evidence synthesis format provided the basis for stakeholder input. Stakeholders rated topics for their potential to inform psychological health care in the military health system. Feasibility scans determined whether topics were ready to be pursued, that is, sufficient literature exists, and duplicative efforts are avoided. Results: We identified 58 intervention, 9 diagnostics, 12 outcome, 19 population, and 24 health services evidence synthesis gaps. Areas included: posttraumatic stress disorder (PTSD) (19), suicide prevention (14), depression (9), bipolar disorder (9), substance use (24), traumatic brain injury (20), anxiety (1), and cross-cutting (14) synthesis topics. Stakeholder input helped prioritize 19 potential PTSD topics and 22 other psychological health topics. To date, 46 topics have undergone feasibility scans. We document lessons learned across clinical topics and research methods. Conclusion: We describe a transparent and structured approach to evidence synthesis topic selection for a health care system using scoping searches, translation into evidence synthesis format, stakeholder input, and feasibility scans.