It is important to ensure that veterans who have experienced military sexual trauma (MST) and have posttraumatic stress disorder (PTSD) have access to trauma-focused treatment. For veterans with serious mental illness (SMI), prior work documents decreased likelihood to receive trauma-focused care. This study focused on evaluating the engagement of Veterans Health Administration (VHA) patients diagnosed with PTSD and who have experienced MST in PTSD specialty care, as well as how this differs for veterans with SMI. Using VHA administrative data, all VHA patients who screened positive for MST prior to fiscal year 2019 (FY2019) were identified (N = 84,503). Based on information from FY2019, measures of psychiatric diagnosis status and VHA treatment participation were generated for all cohort members. Logistic regressions assessed whether there were differences in the likelihood to initiate PTSD care (1+ VHA PTSD specialty clinic encounter) or receive guideline-concordant levels of PTSD specialty care (8+ VHA PTSD specialty clinic encounter) during FY2019. Several other patient characteristics associated with decreased likelihood to receive VHA PTSD specialty servies were identified, including White race and older age. Patient SMI status was not significantly associated with likelihood to initiate or receive guideline-concordant levels of PTSD specialty care. Overall, PTSD treatment initiation was low (11% of veterans with SMI initiated PTSD specialty treatment, as opposed to 10% of veterans without SMI). Additional work is merited to identify ways that VHA is able to overcome barriers to trauma care participation experienced by persons who have experienced MST and been diagnosed with PTSD. (PsycInfo Database Record (c) 2024 APA, all rights reserved).