Abstract Introduction Worse sleep health has been linked with greater substance use among adolescents. However, most studies have only cross-sectionally examined this relationship or examined these longitudinal effects in children with sleep disorders. This study investigates whether childhood sleep is longitudinally associated with adolescent alcohol or marijuana use. Methods We analyzed data from the Fragile Families and Child Wellbeing Study, a longitudinal birth cohort. Parents reported their child’s bedtime at ages 3, 5, and 9, and their child’s average sleep duration at ages 5 and 9. At age 15, adolescents self-reported their bedtime, time in bed, whether they ever drank alcohol without parents, and whether they ever tried marijuana. Only participants with complete data were included (N=1,493). Logistic regression analyses for each substance use outcome were adjusted for age, sex, race, family socioeconomic status, family structure, and caregiver education level. Results Later bedtime at age 3 was longitudinally associated with lower odds of ever drinking alcohol at age 15 (OR=0.73, CI=0.58, 0.91, p<0.01) whereas later bedtime at age 9 was associated with greater odds (OR=1.44, CI=1.10, 1.89, p<0.01). Later bedtime at age 15 was cross-sectionally associated with greater odds of ever drinking alcohol (OR=1.40, CI=1.23, 1.59, p<0.01). Later bedtime at age 5 was associated with greater odds of ever trying marijuana (OR=1.25, CI=1.00, 1.57, p<0.05), as was later bedtime at age 15 (OR=1.34, CI=1.19, 1.51, p<0.01). Additionally, longer sleep duration at age 9 was longitudinally associated with lower odds of ever trying marijuana (OR=0.84, CI=0.74, 0.97, p<0.02). Adolescents who had longer time in bed at age 15 had lower odds of ever drinking alcohol (OR=0.72, CI=0.63, 0.81, p<0.01) and ever trying marijuana (OR=0.89, CI=0.79, 0.99, p<0.04). Conclusion In general, earlier bedtimes and longer sleep duration during childhood and adolescence were associated with lower odds of ever using alcohol or marijuana during adolescence. These results are consistent with current literature indicating that healthy sleep is associated with reduced risk-taking behaviors. Future research should further investigate whether sleep patterns across childhood are linked to decision-making and risk-taking behaviors in adolescence. Support (If Any) R01HD073352 (to LH), R01HD36916, R01HD39135, R01HD40421