ObjectiveApproximately 20% of people with Anorexia Nervosa (AN) and 10% with Bulimia Nervosa (BN) will eventually develop a long‐standing illness. Although there is no set definition for Severe and Enduring eating Disorder (SE‐ED), the common criteria relate to a long duration of the disorder and a number of unsuccessful treatment attempts. Research evidence for treatment of SE‐ED remains limited, thus the objective of this systematic review was to describe different treatment interventions and their effects on SE‐ED‐related outcomes.MethodA systematic search for quantitative treatment studies of adult participants with SE‐ED was conducted in June 2019 (PROSPERO, CRD42018115802) with no restriction on eating disorder type. Altogether, 2,938 studies were included for title and abstract screening.ResultsAfter systematic searches and article screening, 23 studies (3 randomized controlled trials, 3 open‐label studies, 8 naturalistic follow‐up studies, 8 case series and case studies, and 1 partially blinded pilot study) were included in the analysis and data extraction. Methodological quality of the included studies was generally low. Inpatient treatment programs (n = 5) were effective in short‐term symptom reduction, but long‐term results were inconsistent. Outpatient and day‐hospital treatment programs (n = 5) seemed promising for symptom reduction. Drug interventions (n = 5) showed some benefits, especially as adjuvant therapies. Brain stimulation (n = 6) led to improvements in depressive symptoms. Other treatments (n = 2) produced mixed results.DiscussionThis is the first systematic review to examine all of the different treatment interventions that have been studied in SE‐ED. The results will inform future interventions in research and clinical practice.