Military Sexual Trauma (MST) is a pervasive issue among U.S. veterans, linked to substantial mental health consequences including depression, posttraumatic stress disorder (PTSD), anxiety, and suicidality. While these outcomes are well recognized, less is known about how socioecological determinants spanning individual, interpersonal, community, and policy factors influence mental health recovery among survivors. This systematic review aimed to evaluate the evidence on socioecological factors associated with mental health outcomes in veterans with MST. In April 2024, a comprehensive search of MEDLINE, PsycINFO, CINAHL, Web of Science, and EMBASE was conducted following PRISMA guidelines. Eligible studies included U.S. veteran populations reporting MST exposure, at least one mental health outcome, and one or more socioecological determinants such as demographics, military characteristics, and environmental factors. Exclusion criteria were non-U.S. samples, qualitative-only designs, case reports, and review articles. From 16,095 identified records, 216 met inclusion criteria. Quality appraisal and risk of bias were assessed based on Cochrane tools. Most studies employed cross-sectional designs, with fewer longitudinal and interventional research. Preliminary findings demonstrated strong associations between MST and several mental health outcomes, including depression, PTSD, and suicidal ideation. While the influence of individual and interpersonal factors are well-studied, community and policy-level determinants, such as reintegration supports and organizational culture, have been less examined. Findings reveal an overemphasis on individual-level correlates, underscoring the need for multilevel, trauma-informed approaches that incorporate social, environmental, and systemic influences. This review also highlights opportunities for nursing and interdisciplinary teams to integrate socioecological frameworks into practice, research, and policy to enhance holistic recovery and promote resilience among veterans affected by MST.