© 2016 Wiley Periodicals, Inc. Objective: This study assessed loss of control (LOC) eating and eating disorders (EDs) in adolescents undergoing bariatric surgery for severe obesity. Method: Preoperative baseline data from the Teen Longitudinal Assessment of Bariatric Surgery (Teen-LABS) multisite observational study (n = 242; median BMI = 51 kg/m2; mean age= 17; 76% female adolescents; 72% Caucasian) included anthropometric and self-report questionnaires, including the Questionnaire of Eating and Weight Patterns–Revised (QEWP-R), the Night Eating Questionnaire (NEQ), the Beck Depression Inventory (BDI-II), and the Impact of Weight on Quality of Life-Kids (IWQOL-Kids). Results: LOC eating (27%) was common and ED diagnoses included binge-eating disorder (7%), night eating syndrome (5%), and bulimia nervosa (1%). Compared to those without LOC eating, those with LOC eating reported greater depressive symptomatology and greater impairment in weight-related quality of life. Discussion: Before undergoing bariatric surgery, adolescents with severe obesity present with problematic disordered eating behaviors and meet diagnostic criteria for EDs. LOC eating, in particular, was associated with several negative psychosocial factors. Findings highlight targets for assessment and intervention in adolescents before bariatric surgery. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2016; 49:947–952).