The treatment of anorexia nervosa (AN) is often challenging due to medical complications as well as high relapse and mortality rates. Studies about effective treatment options for people with AN are particularly scarce in the adolescent population. This paper is a study protocol for a multi-center cohort study assessing the feasibility, acceptability and efficacy of a new, manualized treatment program, the "Maudsley Model of Anorexia Nervosa Treatment for Adolescents and Young Adults" (MANTRa) compared to psychotherapeutic treatment as usual (TAU).