Repetitive negative thinking (RNT) is associated with eating disorder (ED) symptoms, but few studies have evaluated how RNT may relate to specific ED behaviors (e.g., fasting, binge eating). Furthermore, little research has examined RNT in adolescent girls, a critical population for ED development. Concern over mistakes perfectionism (i.e., preoccupation with and overvaluation of errors) and social appearance anxiety are transdiagnostic risk factors for EDs that may be amplified by RNT, contributing to the development of ED behaviors.