Evidence-based treatments for Posttraumatic Stress Disorder (PTSD) may be enhanced by Functional Analytic Psychotherapy (FAP; Kohlenberg & Tsai, 1991; Tsai et al., 2009). As PTSD can include a variety of problems with interpersonal relationships (e.g., trust of others), manualized treatments may not afford clinicians enough time and flexibility to work on reinforcing client improvements in interpersonal functioning during sessions. Avoidance, which works to alleviate anxiety in the short-term but may lead to distress and complications in the long-term, can manifest in therapy when patients do not return after the initial sessions of treatment or when they block emotional content during targeted emotional processing work. Thus, it is important for clinicians to understand how to use the therapeutic relationship to reduce avoidance symptoms of PTSD in session and reduce dropout rates. FAP can be useful in this regard as an adjunct to efficacious cognitive-behavioral treatments of PTSD. A case study utilizing FAP after a cognitive-behavioral intervention for PTSD is discussed to present an analysis of how FAP may have contributed to client improvements in avoidance symptoms and in interpersonal relationships outside of therapy. Theory behind FAP is discussed to convey how this therapy can be a useful adjunctive treatment for PTSD. (Contains 1 table and 3 figures.)