To date, eating disorder (ED) treatments are lacking for ED patients with psychiatric sequelae of childhood trauma, and successful outcomes are scarce. Therefore, the aim of this study was to explore therapeutic change processes from a patient perspective in relation to good versus poor long-term ED outcome at 1-year follow-up. Outcome categories were based on clinician assessment of ED behavior and diagnoses, body mass index, and Eating Disorder Examination Questionnaire scores. Eleven White, cisgendered female ED patients with childhood trauma were interviewed after a 3-month inpatient treatment: data was analyzed with elements from grounded theory and interpretative phenomenological analysis. The qualitative analysis rendered change-related descriptions (9 subcategories) and obstacles to change (6 subcategories), and 3 process-related domains differentiated good from poor long-term outcome: trauma exposure (4 subcategories), patient agency (6 subcategories), and patient-therapist dynamics (3 subcategories). First, sensory and emotional trauma exposure in good outcome informants was contrasted with avoiding or not addressing trauma and body in poor outcome informants. Second, promotion of patient agency while receiving support in the good outcome group was contrasted to an orientation toward others' needs, distrust in own abilities, and difficulties showing vulnerability in the poor outcome group. Third, poor outcome informants described either a distanced or immersed/idealizing relationship to their therapist, as opposed to more balanced between self-assertion and vulnerability in good outcome informants. Our findings raise new hypotheses that trauma work, fostering patient agency, and focusing on relational dynamics in patient-therapist dyad may be important in producing enduring ED outcomes for these patients. (PsycINFO Database Record (c) 2019 APA, all rights reserved).