Abstract: Social support is important for posttraumatic stress disorder (PTSD) recovery and emerging literature indicate that social support could increase engagement in PTSD therapy. However, there is a need to understand how and why family involvement can increase treatment engagement to inform strategies used in clinical practice. This study explores how individuals with PTSD and family members of individuals with PTSD experience therapy and how social interactions help or hinder therapy engagement. We interviewed 18 U.S. military veterans who had been referred for psychotherapy for PTSD in the Veterans Health Administration and 13 family members and used rapid content analysis to identify themes. We found that engaging in therapy was a family-level decision that Participants expected to improve family life. Veterans were motivated to seek treatment to protect their relationships with loved ones. Family members generally encouraged veterans to seek treatment. Specifically, family members who viewed PTSD as a treatable illness versus a static aspect of the veteran's personality expressed positive attitudes about the effectiveness of therapy for reducing symptoms. Veterans whose social networks included individuals with prior military or trauma-related experiences reported that their loved ones possessed more understanding of PTSD and described positive subjective norms around therapy. Family members are often embedded in the therapy process because PTSD has a profound impact on the family. Positive subjective norms for therapy are created by family encouragement and may influence veteran perceptions about the value of treatment. Family members should be engaged early in mental health therapy and to the extent desired by the patient and family member. (PsycInfo Database Record (c) 2023 APA, all rights reserved).