Background: PTSD is a debilitating disorder impacting approximately 10-30% of veterans within their lifetime. While multiple efficacious treatment for PTSD have been developed, access to and utilization of mental health care remains a significant barrier. Models of health care utilization (e.g., Andersen, 1995; Fortney, 2011) implicate predisposing and enabling factors such as sex, race and/or ethnicity, and socioeconomic status (SES) or socioeconomic deprivation in healthcare access and utilization decisions. Although each of these factors has been examined in isolation, research on race and/or ethnicity and SES is limited, and almost no studies have examined the intersectional impacts of these factors on mental health service utilization among veterans. This study does so, hypothesizing that each will predict mental health service utilization individually, as well as show two and three-way interaction effects. Methods: All variables of interest were derived from the VA medical record, excepting area-level deprivation and geospatial access. Area-level deprivation was determined by linking veteran residential address to the Area Deprivation Index. Geospatial access was calculated by employing kernel density estimation, and linking ZIP-code level values to veteran residential address. All hypotheses were tested using negative binomial regression. Multiple imputation was employed for missingness. Results: Of the 245,574 veterans newly diagnosed with PTSD in 2017 or 2018, 75% attended at least one mental health appointment following diagnosis. The average number of follow-up appointments was 8.9 (mode = 1, median = 3). Sex, race-ethnicity, and area-level deprivation all predicted mental health service utilization individually. There was only one significant two-way interaction effect: identifying as a Black or African American male was positively associated with greater mental health service utilization following diagnosis (0.68, p=.007). There were no three-way interaction effects. Discussion: 1 in 4 veterans with PTSD in this sample did not attend any mental health appointments following diagnosis, highlighting the formidable gap between need and utilization. Furthermore, of those who did attend a follow up appointment, the modal number of appointments was 1, suggesting that entering care is not sufficient to ensure adequate treatment. Sex, race-ethnicity, and area-level deprivation all predicted mental health service utilization individually, but, with a singular exception, did not do so in combination with one another. It is possible that any variance explained by the well-documented compounding effects of societal bias, injustice, and disparities on (mental) health determinants and (mental) healthcare outcomes is more accurately measured by the covariates included in our models, rather than the socially-constructed identities themselves. Taken together, these study findings highlight the need for continued work in lowering barriers to mental health care for this population, as well as a greater understanding of the multitude of factors that influence access to and utilization of services.