Emotion dysregulation has been posited as a key transdiagnostic factor of mental health difficulties, including eating disorders. However, how this transdiagnostic factor interacts with the disorder-specific factor of weight and shape concerns remains unclear. The current study examined whether emotion dysregulation is associated with eating disorder behaviors over and above the association between weight and shape concerns and whether these two factors interacted. The current study used data from two samples, a community sample of high school students (n = 2699), and a clinical sample of adolescents receiving outpatient treatment for an eating disorder (n = 149). Participants completed self-report measures on their eating behaviors, weight/shape concerns, and emotion dysregulation. Findings showed that emotion dysregulation had a unique association with engaging in binge eating and purging (community sample only). Weight and shape concerns were found to have a unique association with engaging in binge eating, fasting, purging, and driven exercise (community sample only). Additionally, weight and shape concerns moderated the association between emotion dysregulation and the probability of engaging in binge eating and driven exercise, whereby the strongest association between emotion dysregulation and these behaviors were observed among adolescents with the lowest levels of weight and shape concerns. Regarding the frequency of eating disorder behaviors, emotion dysregulation had a unique association with severity of binge eating and fasting. Weight and shape concerns were uniquely associated with severity of fasting and driven exercise (community sample only). Findings suggest that emotion dysregulation is a distinct factor of eating disorder behaviors among adolescents.