IMPORTANCE Severe obesity is associated with mobility limitations and higher incidence of multijoint musculoskeletal pain. It is unknown whether substantial weight loss improves these important outcomes in adolescents with severe obesity. OBJECTIVE To examine the association of bariatric surgery with functional mobility and musculoskeletal pain in adolescents with severe obesity up to 2 years after surgery. DESIGN, SETTING, AND PARTICIPANTS The Teen-Longitudinal Assessment of Bariatric Surgery Study is a prospective, multicenter, observational study, which enrolled 242 adolescents (≤19 years of age) who were undergoing bariatric surgery from March 2007 through February 2012 at 5 US adolescent bariatric surgery centers. This analysis was conducted in November 2015. INTERVENTIONS Roux-en-Y gastric bypass (n = 161), sleeve gastrectomy (n = 67), or laparoscopic adjustable gastric band (n = 14). MAIN OUTCOMES AND MEASURES Participants completed a 400-mwalk test prior to bariatric surgery (n = 206) and at 6 months (n = 195), 12 months (n = 176), and 24 months (n = 149) after surgery. Time to completion, resting heart rate (HR), immediate posttest HR, and HR difference (resting HR minus posttest HR) were measured and musculoskeletal pain concerns, during and after the test, were documented. Data were adjusted for age, sex, race/ethnicity, baseline body mass index (calculated as weight in kilograms divided by height in meters squared), and surgical center (posttest HR and HR difference were further adjusted for changes in time to completion). RESULTS Of the 206 adolescents with severe obesity included in the study, 156 were female (75.7%), the mean (SD) age was 17.1 (1.6) years, and the mean (SD) body mass index was 51.7 (8.5). Compared with baseline, significant improvements were observed at 6 months for the walk test time to completion (mean, 376 seconds; 95%CI, 365-388 to 347 seconds; 95%CI, 340-358; P < .01), resting HR (mean, 84 beats per minute [bpm]; 95%CI, 82-86 to 74 bpm; 95%CI, 72-76), posttest HR (mean, 128 bpm; 95%CI, 125-131 to 113 bpm; 95%CI, 110-116), and HR difference (mean, 40 bpm; 95%CI, 36-42 to 34 bpm; 95%CI, 31-37). These changes in time to completion, resting HR, and HR difference persisted at 12 months and 24 months. Posttest HR further improved from 6 months to 12 months (mean, 113 bpm; 95%CI, 110-116 to 108 bpm; 95%CI, 105-111). There were statistically significant reductions in musculoskeletal pain concerns at all points. CONCLUSIONS AND RELEVANCE These data provide evidence that bariatric surgery in adolescents with severe obesity is associated with significant improvement in functional mobility and in the reduction of walking-related musculoskeletal pain up to 2 years after surgery.