Eating disorder patients with posttraumatic stress disorder have worse treatment results regarding their eating disorder than patients without posttraumatic stress disorder. Many eating disorder patients with co-morbid posttraumatic stress disorder symptoms are not treated for posttraumatic stress disorder symptoms during an underweight state. We propose that treatment of posttraumatic stress disorder is possible for underweight patients and that their trauma symptoms decrease with the use of Imagery Rescripting. We also investigated whether treatment of trauma influences eating disorder pathology in general and the process of weight gain specifically.