Eating disorders and posttraumatic stress disorder (PTSD) are debilitating conditions that frequently co-occur. Although the two disorders have different clinical presentations, they share associated features, including cognitive disturbances, emotion dysregulation, dissociation, and impulsivity. We hypothesized that reductions in PTSD symptoms following cognitive processing therapy (CPT) and its treatment components (CPT without the written account or the written account only) would be associated with improvements in symptoms common to PTSD and eating disorders. Participants in the current investigation included women with PTSD (N = 65) who reported a history of rape or physical assault, were in a randomized dismantling study of CPT, and completed the Eating Disorder Inventory-2 (EDI-2) at pre- and posttreatment. Latent growth modeling results indicated that decreases in PTSD symptom scores were significantly associated with reductions in the Impulse Regulation, Interoceptive Awareness, Interpersonal Distrust, Ineffectiveness, and Maturity Fears subscales of the EDI-2. Thus, PTSD treatment affected symptoms shared by PTSD and eating disorders. Currently, there are no clear guidelines for treatment of comorbid PTSD and eating disorders. Traditional CPT may impact symptoms common to both, but additional therapy may be needed for specific disordered eating attitudes and behaviors.