There is growing evidence of prior experiences of trauma and trauma-related symptoms among people with eating disorders; however, there is little understanding as to how post-traumatic stress disorder (PTSD) and exposure to traumatic events affect treatment outcomes. Without this knowledge, eating disorder clinicians are unable to tailor treatment to ensure good outcomes for the large percentage of this population that is affected by PTSD and trauma. This systematic review aimed to identify how PTSD and trauma exposure influence outcomes in eating disorder treatment. Systematic searches of PsycINFO, MEDLINE, PubMed, and Scopus databases identified 16 articles that met the inclusion criteria. The results indicated a negative effect on rates of eating disorder treatment completion and eating disorder psychopathology posttreatment. These findings were evident across studies that investigated the impact of a history of traumatic events as well as studies that investigated the impact of the presence of trauma-related symptoms seen in PTSD. Several methodological limitations were identified in the literature. These include: heterogeneous and unstandardized measures of PTSD and trauma, high attrition rates with follow-up, and insufficient data to enable comparisons by treatment setting, diagnostic presentation, and type of trauma exposure. The findings of this review have implications for future research and clinical care, including the importance of considering PTSD and trauma in assessment, treatment planning, and provision of both trauma-informed care and trauma-focused treatments for individuals with eating disorders.