PTSD is a mental health condition that affects many people over the course of their life (National Comorbidity Survey, 2005), including veterans (Litz & Schlenger, 2009). However, many do not experience clinical levels of distress and some experience posttraumatic growth (PTG) resulting from such an event (Tedeschi, Park, & Calhoun, 1998). The Psychological Flexibility Model, of which Acceptance and Commitment Therapy (ACT; Hayes, Strosahl, & Wilson, 1999) is based, may help explain these phenomena. The purpose of this study was to examine these relationships utilizing a measure simultaneously assessing psychological flexibility and inflexibility. It was hypothesized that psychologically inflexible behaviors would predict PTSD symptom severity, while flexible behaviors would predict PTG. Furthermore, each of psychological inflexibility and flexibility would account for unique variance in PTSD symptom severity and PTG, respectively. Finally, the domains of ACT were examined to assess the strength each component has in the maintenance of these experiences. Results indicated that both psychological inflexibility and flexibility predicted PTSD symptoms and PTG, respectively, and each predicted unique variance in these experiences. Of the individual components, cognitive fusion, experiential avoidance, inaction, and lack of contact with the present moment all contributed to PTSD symptom severity, while values clarity, lack of contact with the present moment, and present moment awareness contributed to PTG. These results suggest the psychological flexibility model overall is consistent with the experience of PTSD symptoms and the posttraumatic growth. Though further experimental methods are needed, the application of psychological flexibility through ACT could enhance PTSD treatments.