Introduction: We aimed to study the effects of the glucagon-like peptide-1 receptor agonist exenatide on behavioral outcomes in children and adolescents with obesity. Methods: This study reports pre-specified secondary outcomes of a randomized, double-blind, placebo-controlled trial in adolescents with obesity, aged 10-18 years old. Participants (n=44) were randomized to six months treatment with exenatide or placebo, along with a lifestyle intervention consisting of nutritional advice from a dietitian and sessions with a psychologist to optimize physical activity. Change in choices of food and drink, portion sizes, meal frequency, sleep, screen time, and physical activity were assessed by 6-minute walking test, accelerometry and questionnaires. Results: Exenatide treatment was associated with improved adherence to choices of recommended food and drinks (score change 4.34, 95% CI 1.05 – 7.63, p=0.01, Hedges’ g 0.82, 95% CI 0.17 – 1.49), decreased portion size (score change -4.05, 95% CI -6.51 – -1.58, p=0.002, Hedges’ g -1.29, 95% CI -2.13 – -0.45), and increased self-reported physical activity (1.82 hours, 95% CI 0.68 – 2.96, p=0.002 Hedges’ g 0.97, 95% CI 0.33 – 1.62), while no differences in meal frequency, snacking, sleep, screen time, objectively measured physical fitness or activity were found. Conclusion: Exenatide treatment was associated with modest improvements in selected self-reported dietary behaviors, including improved adherence to recommended food and drink choices and reduced portion sizes, as well as increased self-reported physical activity, although no changes were observed in objective measures of physical activity or other lifestyle factors.