Background: Posttraumatic stress disorder (PTSD) is the most common psychiatric service-connected condition among women Veterans, yet many women Veterans do not receive evidence-based psychotherapies for PTSD. PTSD and insomnia disorder are highly comorbid in women Veterans and research suggests that insomnia is a risk factor for PTSD development and severity, while healthy sleep is associated with improved mood, daytime functioning, enhanced learning, and increased emotion regulation. Addressing insomnia symptoms in women Veterans may offer an early point of intervention to reduce insomnia and some PTSD symptoms, while also providing a novel approach to improve patient engagement in PTSD treatments. Significance/Impact: Women's health and mental health (specifically PTSD) are research priority areas for VA. Women Veterans experience multiple barriers to PTSD treatments including: perceived stigma, severity of symptoms/emotion dysregulation, and scheduling/time constraints. Providers report delaying PTSD treatments due to perceptions of patients' “unreadiness” to begin PTSD treatments. Cognitive Behavioral Therapy for Insomnia (CBT-I; first-line treatment for insomnia) is perceived as highly acceptable to women Veterans, improves sleep in individuals with comorbid psychiatric conditions, offers a brief intervention alternative to psychotherapy protocols for PTSD, and is widely disseminated within VA. Innovation: No previous studies have examined the impact of trauma-informed CBT-I on sleep and psychiatric symptoms among women Veterans with comorbid insomnia disorder and PTSD. The project will utilize a mixed methods approach, gathering novel information from women Veterans to identify facilitators of and barriers to PTSD and insomnia treatments among women Veterans. While there are indications that CBT-I may serve as a preparatory treatment to other evidence-based psychotherapies, this would be the first study to utilize a trauma-informed CBT-I protocol and examine mental health treatment engagement as a primary outcome. Specific Aims: The specific aims are to: 1) Iteratively refine the structure and materials of trauma-informed CBT-I in preparation for a pilot trial, 2) Pilot test the effects of trauma-informed CBT-I on PTSD treatment readiness and engagement in a sample of women Veterans, and 3) Examine potential mechanisms underlying variations in PTSD treatment readiness and engagement over time among women Veterans. Methodology: The proposed project will be carried out within VAGLAHS. In Aim 1, women Veterans will sequentially receive the trauma-informed CBT-I protocol. We will obtain qualitative feedback from each participant, and make needed refinements before administering the protocol to the next participant (anticipated n=5). In Aim 2, women Veterans with comorbid insomnia disorder and PTSD will be recruited to participate in a behavioral intervention study and eligible participants will be randomly assigned to either trauma-informed CB...