Insufficient sleep is a risk factor for depression, suicidality, and substance use, yet little is known about gender, ethnic, and community-level differences in sleep and its associated outcomes, especially during adolescence. Further, much of the prior work has compared groups of teens getting plenty as opposed to insufficient amounts of sleep rather than examine sleep hours continuously. The present study examined adolescent weekday self-reported sleep duration and its links with hopelessness, suicidality, and substance use in a suburban community with very early high school start times. We utilized a large (N = 27,939, 51.2% female) and ethnically diverse sample of adolescents from the 2009 Fairfax County (Virginia) Youth Survey, an anonymous, self-report, population-level survey administered to all 8th, 10th and 12th grade students in public schools in the county. High-school students reported an average 6.5 h of sleep per school night, with 20% obtaining ≤5 h, and only 3% reporting the recommended 9 h/night. Females and minority youth obtained even less sleep on average, and the reduction in sleep in the transition from middle school to high school was more pronounced for females and for Asian students. Hierarchical, multivariate, logistic regression analyses, controlling for background variables, indicated that just 1 h less of weekday sleep was associated with significantly greater odds of feeling hopeless, seriously considering suicide, suicide attempts, and substance use. Relationships between sleep duration and suicidality were stronger for male teens, and sleep duration was more associated with hopelessness for white students compared to most ethnic minority groups. Implications for intervention at multiple levels are discussed.