Cognitive inflexibility and attention to detail bias represent a promising target in eating disorder (ED) treatment. While prior research has found that adults with eating disorders exhibit significant cognitive inflexibility and heightened attention to detail, less is known about these cognitive impairments among adolescents, and across EDs transdiagnostically. To address this gap, adolescent females ( = 143) from a residential ED program with anorexia nervosa, bulimia nervosa, or other specified feeding or eating disorder completed the Detail and Flexibility Questionnaire (DFlex) and measures of ED and general psychopathology. Transdiagnostically, adolescents with EDs scored higher than an archival sample of healthy control adolescents on both cognitive rigidity ( < .001; Cohen's = 1.92) and attention to detail ( < .001; Cohen's = 1.16). These cognitive impairments were significantly associated with severity of eating pathology, and these relationships existed independent of age, duration of illness, or body mass index (BMI). Our findings suggest cognitive inflexibility and heightened attention to detail occur transdiagnostically in adolescents with eating disorders and are unlikely to be a scar of the disorder. Future prospective research is needed to determine whether these cognitive styles represent an endophenotype of eating disorders.