Abstract: Combat veterans are at high risk for suicide; consequently, it is paramount to examine factors that may relate to lower levels of suicide among this population. This study examined if somatic depression or affective depression symptoms mediate the relationship between posttraumatic stress disorder (PTSD) and suicidal behaviors in a treatment-seeking sample of post-9/11 combat veterans. Fluid Vulnerability Theory was utilized as a theoretical framework. We conducted two PROCESS simple mediation models with PTSD as the predictor, affective depression and somatic depression as the mediators, and suicidality as the dependent variable, while controlling for generalized anxiety. We found that affective depression significantly mediated the relationship between PTSD and suicidal behaviors, while somatic depression symptoms did not. In both simple mediation models, the direct effect of PTSD to suicidal behaviors was significant. This study provides a unique perspective on suicidal behavior in combat veterans and offers insights into the nature of mediating relationships between affective depression and somatic depression and suicidal behavior.