Objective: The current investigation sought to explore the impact of the comorbidities of substance use disorder (SUD), major depressive disorder (MDD), and borderline personality disorder (BPD) on the trajectory of intimate partner violence (IPV)-related posttraumatic stress disorder (PTSD) symptoms across a 6-month follow-up period in IPV survivors who seek shelter. Research has found significant comorbidity of SUD, MDD, and BPD with PTSD (see Green et al., 2006; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995; Pagura et al., 2010); however, little to no research has explored these relationships in this unique population over time. Method: A sample of 147 residents of battered women’s shelters completed study measures at baseline, 1 week, and 3 and 6 months following shelter stay. Participants completed measures assessing for demographics, abuse, and Diagnostic and Statistical Manual of Mental Disorders (4th edition, text revision) diagnoses. Results: Results of latent growth modeling with the time-invariant covariates of SUD, MDD, and BPD yielded a significant effect of SUD (β = .002, p = .007) on the slope of IPV-related PTSD symptoms controlling for IPV victimization. Significant effects were not identified for BPD (β = .001, p > .05) or MDD (β = .002, p > .05). Results suggest IPV survivors with SUD demonstrated less improvement in PTSD symptoms over 6 months after they left shelter as compared to women without SUD. Conclusion: Findings emphasize the deleterious effects of SUD, above and beyond MDD and BPD, on IPV-related PTSD and highlight the need for assessment and treatment of SUD and PTSD simultaneously in residents of battered women’s shelters. Clinical Impact Statement: Findings suggest the need to go beyond standard shelter services to more effectively address and treat co-occurring SUD-PTSD in IPV survivors.