Abstract: Military sexual trauma (MST) affects approximately 2% and 36% of male and female veterans, respectively, (e.g., Allard, Gregory, Klest, & Platt, 2011). Although the deleterious consequences of MST have been clearly established, few studies have explored treatment effectiveness for this population. Using archival data from a residential treatment program, the current study explored the effectiveness of cognitive processing therapy (CPT) in treating full or subthreshold posttraumatic stress disorder (PTSD) to compare U.S. veterans reporting an MST index trauma (MST-IT) to those without MST-IT. Of the 481 participants, 40.7% endorsed MST-IT. Multiway frequency analyses were utilized to compare men and women with and without MST on baseline demographic variables. Hierarchical linear models were constructed to investigate treatment outcome by MST status and sex. Results showed that 44.8%, 23.8%, and 19.6% of the variation in clinician- and self-reported PTSD and depression symptoms were explained by three models. Scores on all outcome measures significantly decreased over time for both groups. Additionally, women demonstrated a sharper decrease in PTSD symptoms over time than men. Lastly, men who reported MST-IT had higher PTSD symptoms than men without MST-IT on average. With no control group or random assignment, preliminary findings suggest residential treatment including CPT may be effective for MST-IT regardless of sex.