PURPOSE: Evaluate Bright 1 Bodies (B1B) intervention for sedentary adolescents with type 1 diabetes (T1D) for safety and health outcomes. METHODS: Eighteen sedentary adolescents with T1D (age 13.7±2.3y, female 67%, Black/Latino 67%, BMI 88±12%’ile, annual income 33% <$20k, 55% <$40k, A1c 9.5±2.3%, 79.9±25.1 mmol·mol-1) participated in group exercise classes (35min @ 60-80%HRmax) and self-management education 1x·wk-1 for 12wk. Anthropometrics, glycemic control,brachial blood pressure, fasting lipids, and cardiopulmonary fitness (15m Progressive Aerobic Cardiovascular Endurance Run modified to slower starting speed, MPACER) were compared at baseline and 12wk using repeated measures ANCOVA for intent-to treat (n=18) and per protocol completers (attended ≥8 sessions, n=10). RESULTS: Blood glucose (BG) dropped from 12.16±4.35 mmol·L-1 at start of exercise to 9.16±2.94 mmol·L-1 at completion (p<0.01). Hypoglycemia (BG<3.89 mmol·L-1 with signs and/or symptoms) occurred once (0.6%). Average of 8.6±12.1g carbohydrates were required before, during, and/or after exercise. In the total sample (n=18) there were no changes in BMI, A1c, cardiopulmonary fitness, body fat, waist circumference, mean arterial pressure, or lipid profile (p>0.05). In the 10 completers, cardiopulmonary fitness improved (30.0±17.3vs37.1±20.8 MPACER shuttles, p=0.04), LDL increased but within normal ranges (2.23±0.54vs2.52±0.59 mmol·L-1, p=0.02), and all other variables were unchanged (p>0.05). CONCLUSION: B1B was safe for sedentary adolescents with T1D and improved cardiopulmonary fitness among completers. Exercise sessions decreased BG into ADA target range (3.9-10.0 mmol·L-1) with low risk of hypoglycemia and minimal need for supplemental carbohydrates (~35 kcals per 35min exercise session). However, overall glycemic control remained poor and BMI overweight, suggesting this at-risk population needs more intensive interventions. Support: NIH-T32DK097718; Friends of Yale New Haven Children’s Hospital; Yale School of Nursing Biobehavioral Lab; NEACSM Young Investigator Award; NIH-UL1TR000142