The need for evaluation capacity building (ECB) in military psychological health is apparent in light of the proliferation of newly developed, yet untested programs coupled with the lack of internal evaluation expertise. This study addresses these deficiencies by utilizing Preskill and Boyle's multidisciplinary ECB model within a post-traumatic stress disorder treatment program. This model outlines a theoretical framework, offers practical strategies, and emphasizes both context and culture, which are paramount in military health-care settings. This study found that the model provides a highly applicable ECB framework that includes ways to identify ECB objectives, tailor activities, and understand outcomes. While there was high utilization of ECB activities by program staff, there was misaligned evaluative thinking, which ultimately truncated sustainable evaluation practice. Based on this research, evaluators can better understand how to provide an ECB intervention in a complex cultural and political environment and assess its effectiveness.