Veterans involved with the criminal justice system represent a particularly vulnerable population who experience high rates of both posttraumatic stress disorder (PTSD) and substance use disorders (SUD). This study sought to investigate whether having co-occurring SUD is a barrier to PTSD treatment. This is a retrospective observational study of a national sample of justice-involved veterans served by the Veterans Health Administration Veterans Justice Outreach program who had a diagnosis of PTSD (N = 27,857). Mixed effects logistic regression models with a random effect for facility (N = 141 medical centers) were utilized to estimate the odds of receiving each type of PTSD treatment as a function of having a SUD diagnosis. Results indicate that a majority of veterans with PTSD served by the Veterans Justice Outreach program have an SUD diagnosis (73%), and having a co-occurring SUD was associated with higher odds of receiving PTSD treatment, after adjusting for demographic differences. Although not without limitations, these results suggest that among justice-involved veterans enrolled in the Veterans Health Administration with PTSD, having an SUD comorbidity is not a barrier to PTSD treatment and may in fact facilitate access to PTSD treatment.