Abstract: Shame and the tendency to ruminate have been linked to the onset and persistence of Post-Traumatic Stress Disorder (PTSD) and Major Depressive Disorder (MDD). We examined the relationship between shame, current levels of rumination, and a potential protective factor, self-compassion, and symptoms of PTSD and depression among military veterans and active-duty service members (n = 307). Shame and current levels of rumination were both strongly correlated with symptoms of PTSD and depression. Moreover, rumination was a predictor of both symptoms of PTSD and depression and mediated the relationship between shame and symptoms of PTSD and depression. Self-compassion significantly moderated the relationship between both shame and rumination, and symptoms of PTSD, but not symptoms of depression. These findings highlight rumination as not only a robust risk factor for PTSD and MDD, but also a mediator between shame and symptoms of PTSD and MDD. Finally, self-compassion may serve as a protective factor against trauma-related shame and rumination and symptoms of PTSD.