Sleep disturbance is a unique, yet understudied, risk factor for suicidal thoughts and behaviors (STBs). The present study sought to explore the relationship between suicidal ideation (SI) and self-reported sleep disturbance in a sample of adolescents in an intensive outpatient program targeting suicidality (N = 691). Analyses conducted include paired samples t tests, multiple linear regression, and analysis of variance to examine group differences in sleep disturbance over time. Sleep disturbance and SI were associated at each timepoint, and sleep disturbance at admission predicted SI at discharge. Those with the most severe SI at discharge indicated increased sleep disturbance relative to admission, whereas those reporting no SI at discharge nearly resolved all sleep difficulties. Future studies should utilize objective sleep measures, longitudinal assessments, and include a more diverse sample to better inform the relationship of sleep and SI. These findings suggest that directly managing sleep disturbance during treatment could decrease the risk of STBs.