Social support is closely linked to health, but little is known about United States (U.S.) veterans' social support over time and factors that may influence their support trajectories. This study investigates social support over time for U.S. men and women Post-9/11 veterans in relation to trauma history and gender. A secondary analysis of longitudinal cohort data from the Survey of Experiences of Returning Veterans (SERV), which employed a repeated-measures longitudinal design using five waves of data (baseline, 3, 6, 9, 12 months) with 672 combat veterans. Results from random intercept multilevel models found no significant gender differences in social support over time. Veterans with complex trauma histories were at risk for lower social support across waves. A stability trend was also observed; specifically, at baseline, veterans who started with high support maintained their level over time whereas veterans who started with deficits in social support remained low over time. Veterans identifying as African American or Latinx, and those with lower annual incomes, reported lower support compared to White and higher-income veterans. Furthermore, low social support was significantly associated with severe posttraumatic stress symptoms and active suicidal ideation across 12 months. SERV utilized a nonrandom sampling method that may reduce generalizability of findings. There is also potential for residual confounding by factors related to both social support levels and time since discharge that were not available in this data set. Findings have implications for developing clinical and community interventions intended to support veterans as they transition back to the community. (PsycInfo Database Record (c) 2023 APA, all rights reserved).