Nearly 70% of adolescents have chronic sleep problems (quality, quantity, and/or altered circadian rhythm). Adolescents with type 1 diabetes (T1D) are subject to nocturnal blood glucose fluctuations that may result in restless sleep and require self-care that disrupts sleep. Deficient sleep may also contribute to insulin resistance. Few studies of sleep characteristics and their association with glycemic control have been conducted. Our aim was to describe sleep characteristics in adolescents with T1D and its relationship with glycemic control. Adolescents with T1D (ages 10-16) were recruited from the Yale Program. For 7 days, participants wore a wrist actigraph, which was used to calculate sleep/wake cycles using 30-second epochs, and a continuous glucose monitor (CGM). The Pittsburgh Sleep Quality Index (PSQI) was used to assess subjective sleep reports. The sample included 30 participants age 13.4+1.9, 67.9% female, 29.2% minority, BMI percentile 75+25%, diabetes duration 7.4+ 4.5 years, and 97% on insulin pumps. Hemoglobin A1c (A1c) levels (8.29+1.38%) and CGM (46.3+14.9% time in hyperglycemia) indicated poor glycemic control. Actigraphy showed inadequate total sleep time (7.33+19 hours), but good sleep efficiency (80.0+20.3%). Higher MESOR (rhythm adjusted mean) (r=0.25) and lower circadian quotient (r=-0.31) were associated with higher A1c. Greater circadian quotient was associated with more glucose variability (r=0.41). Greater WASO (wake after sleep onset) was associated with higher glucose (r=0.26), HBGI (high blood glucose index) (r=0.27), and more hyperglycemia (r=0.25). Higher MESOR was associated with lower LBGI (low blood glucose index) (r=-0.39) and less hypoglycemia (r=-0.42). Higher amplitude was associated with lower LBGI (-0.35) and less hypoglycemia (r=-0.39). These results suggest that insufficient sleep is common among adolescents with T1D and is associated with poorer glycemic control. Further research is required to determine if improving sleep will improve glycemic control. Disclosure M. Grey: None. K. Rechenberg: None.