Objective: The primary objective of this study was to evaluate the prevalence of multiple types of sleep problems in young adolescents with ADHD. Method: Adolescents comprehensively diagnosed with ADHD (N = 262) and their caregivers completed well-validated measures of sleep problems and daytime sleepiness. Participants also completed measures related to medication use, comorbidities, and other factors that could predict sleep problems. Results: Daytime sleepiness was by far the most common sleep problem, with 37% of adolescents meeting the clinical threshold according to parent report and 42% according to adolescent report. In contrast, prevalence rates for specific nighttime sleep problems ranged from 1.5% to 7.6%. Time spent in bed, bedtime resistance, ADHD inattentive symptoms, and Sluggish Cognitive Tempo (SCT) symptoms were significant in the final model predicting daytime sleepiness. Conclusion: Adolescents with ADHD commonly experience problems with daytime sleepiness that may significantly affect their functioning, but this may not be directly attributable to specific sleep problems.