ObjectiveThis pilot study investigated the feasibility and preliminary efficacy of the metacognitive training for eating disorders (MCT‐ED) program in adolescents with anorexia nervosa (AN). We report attrition and subjective evaluation as well as changes to cognitive flexibility, perfectionism and eating disorder pathology relative to waitlist controls.MethodFemale (n = 35, aged 13–17 years) outpatients with a diagnosis of AN (n = 20) or atypical AN (n = 15) completed baseline measures of cognitive flexibility, perfectionism, and eating disorder pathology (May 2020–May 2022). Participants were randomly allocated to either treatment‐as‐usual (TAU) plus MCT‐ED or TAU waitlist condition. All participants completed post‐intervention and 3‐month follow‐up questionnaires.ResultsThe MCT‐ED condition had a treatment attrition rate <15%. Participants provided positive evaluation of the program. There were large between groups differences favoring MCT‐ED at post‐intervention and 3‐month follow‐up for concern over mistakes perfectionism (respective ds = −1.25, 95% CI [−2.06, −.45]; −.83, 95% CI [−1.60, .06]) with a significant group difference post‐intervention but not 3‐month follow‐up.DiscussionFindings provide tentative support for the feasibility of MCT‐ED as an adjunct intervention for young people with AN, however replication is needed with a larger sample size to further explore its efficacy.Public significanceMetacognitive training for eating disorders (MCT‐ED) is a feasible adjunct intervention for adolescents with anorexia nervosa. The intervention, which targets thinking styles and is delivered online by a therapist, received positive feedback, had high treatment retention, and led to reductions in perfectionism by the end of treatment compared to wait‐list controls. Although these gains were not sustained long‐term, the program is suitable adjunct intervention for young people with eating disorders.