Previous research has demonstrated that sleep disturbances show little improvement with evidence-based psychotherapy for posttraumatic stress disorder (PTSD); however, sleep improvements are associated with PTSD treatment outcomes. The goal of the current study was to evaluate changes in self-reported insomnia symptoms and the association between insomnia symptoms and treatment outcome during a 3-week intensive treatment program (ITP) for veterans with PTSD that integrated cognitive processing therapy (CPT), mindfulness, yoga, and other ancillary services. As part of standard clinical procedures, veterans (N = 165) completed self-report assessments of insomnia symptoms at pre- and posttreatment as well as self-report assessments of PTSD and depression symptoms approximately every other day during treatment. Most veterans reported at least moderate difficulties with insomnia at both pretreatment (83.0%-95.1%) and posttreatment (69.1-71.3%). Statistically significant reductions in self-reported insomnia severity occurred from pretreatment to posttreatment; however, the effect size was small, d = 0.33. Longitudinal mixed-effects models showed a significant interactive effect of Changes in Insomnia × Time in predicting PTSD and depression symptoms, indicating that patients with more improvements in insomnia had more positive treatment outcomes. These findings suggest that many veterans continued to struggle with sleep disruption after a 3-week ITP, and successful efforts to improve sleep could lead to better PTSD treatment outcomes. Further research is needed to establish how adjunctive sleep interventions can be used to maximize both sleep and PTSD outcomes.