Sleep disturbances are common features of bipolar disorder (BD), yet little is known about trajectories of sleep disturbances in youth with BD. Using longitudinal data, this study assessed the stability of sleep disturbances and their ability to predict symptom progression in adolescents diagnosed with BD compared to controls. Thirteen- to 19-year-olds meeting diagnostic criteria for BD I (n = 19, 16.2 ± 1.75 years, 57.9 % female, 68.4% Caucasian) and psychiatrically healthy age-comparable controls (n = 21, 15.7 ± 1.48 years. 52.4% female, 57.1% Caucasian) were assessed for sleep onset latency, number of awakenings, and wake time, separately for weekdays and weekends using a self-report questionnaire. Sleep indices and symptoms of mania (Young Mania Rating Scale) and depression (Children's Depression Rating Scale) were assessed at two time points, T1 and T2, approximately 12 months apart. Correlations were used to examine stability of sleep indices across time points and regression models to examine the effects of T1 sleep on T2 symptoms. Adolescents with BD showed low stability on most sleep indices, whereas controls showed high stability on all sleep indices. After controlling for T1 depression symptoms, more T1 weekend awakenings and weekend wake time predicted significantly greater T2 depression symptoms in youth with BD but not in controls. No significant associations were found between T1 sleep and T2 mania symptoms. These findings suggest that increased awakenings and wakefulness on weekends may represent an important therapeutic target for reducing depression in adolescents with BD.