Abstract: Objective: The present study examined whether self-blame from sexual assault while in the military mediated associations between institutional betrayal from sexual assault and past-week depressive and posttraumatic stress disorder (PTSD) symptoms. Method: All participants were cisgender women who were former or current U.S. service members (N = 153; M = 32.37 years; SD = 8.35) who endorsed sexual assault while in the military. On average, sexual assault had occurred 7.07 years (SD = 7.62) earlier. Participants completed an online survey in which they were asked about institutional betrayal stemming from their military sexual assault, and self-blame from their sexual assault experience, in addition to depressive and PTSD symptoms. Results: Self-blame that occurred from sexual assault mediated the relationship between institutional betrayal attributed to sexual assault, and depressive symptoms and PTSD symptoms. Conclusions: Findings point to the importance of self-blame from sexual assault in understanding the association between institutional betrayal and mental health among military women who report sexual assault while in the military. These findings lend support to betrayal trauma theory (Freyd, 1994). These findings also have implications for those who work with military women who are survivors of sexual assault and suggest that addressing self-blame associated with sexual assault may be important for treatment.