Although effective treatments for PTSD exist, high rates of treatment dropout and sub-optimal response rates remain common. Incorporating family members in treatment represents one avenue for improving outcomes and providing Veteran-centered care, and surveys of Veterans in outpatient VA PTSD care indicate that 80% desire family involvement. The VA has invested many years and millions of dollars on the dissemination of Cognitive Processing Therapy (CPT) and Prolonged Exposure (PE) for PTSD. A family-based intervention that complements these two first-line treatments would capitalize on existing treatment infrastructure while also potentially boosting outcomes and retention. Preliminary testing of the proposed Brief Family Intervention (BFI) resulted in 50% less dropout from CPT/PE among Veterans whose family members received the BFI. There was also a large impact on PTSD symptoms at 16 weeks (d = 1.12) in favor of the BFI group. The goal of this study is to test the effectiveness of the BFI among a fully-powered sample. One hundred Veteran-family member dyads (n = 200) will be recruited. Veterans will be beginning a course of usual-care CPT or PE at one of two VA sites. Family members will be randomized to receive or not receive the BFI, a two-session psychoeducational and skills-based protocol. PTSD symptom severity and treatment retention will be the primary outcomes. Assessments will be conducted by independent evaluators at baseline, 6-, 12-, 18-, and 26-weeks. Veterans whose family members receive the BFI are expected to have lower dropout and a greater rate of change in their PTSD symptoms compared to Veterans whose family members do not receive the BFI. If the BFI is found to increase the effectiveness of and retention in CPT/PE, it will be a highly appealing option for incorporating families into Veterans' PTSD care.