Objective: To assess the outcome of adolescents with anorexia nervosa (AN) about 20 years after first treatment. Methods: Sixty-two women diagnosed with AN during adolescence were invited to participate. Of these 62 patients, 38 agreed to participate and were assessed with a battery of questionnaires and interviews. A control group of 30 women of similar age was also assessed. Results: Of the patients who completed the full assessment, 13 (34%) presented some degree of eating disorder (ED) at follow-up (10 (26%) met full Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) criteria for an ED and 3 (8%) showed partial remission of an ED). The remaining 25 (66%) patients had fully recovered from AN. The duration of untreated illness before admission was significantly associated with an increased risk of a current ED (odds ratio (OR) = 3.334 (1.3–8.7); p = .014). Of the patients who had recovered totally from their ED, 24% showed another psychiatric disorder. This percentage rose to 70% in patients with a current ED. Conclusion: Sixty-six percent of adolescents who completed the assessment achieved remission of their AN. Comorbidity was more common in the current ED group. The variable that best predicted complete remission was the number of years without treatment, showing the importance of detection and early intervention.