Objective The current study aimed to develop and evaluate a motivational school-based intervention for adolescent sleep problems. Methods The intervention was implemented in three co-educational secondary schools in Adelaide, South Australia. Two year-11 Psychology classes from each school participated, with one as the intervention class (N =53) and one as the control class (N =51). Students in the intervention classes attended four 50-min sleep education classes, held once per week. The lessons were modified from those of Moseley and Gradisar [23] to incorporate a motivational interviewing framework. Students completed an online questionnaire battery measuring school day and weekend sleep parameters, daytime sleepiness, and depression at pre- and post-program and follow-up, and completed motivation to change questionnaires during the program. Results Students in the intervention group significantly increased their knowledge about sleep relative to the control group (p =0.001). During the intervention, students’ motivation to regularize their out-of-bed times improved (p =0.03), and there was a trend towards improved motivation to increase average total sleep time (p =0.11). But despite improvements in sleep and daytime functioning for adolescents in the program group (p <0.05), these changes were not significantly different from the control group (all p >0.05). Conclusions School-based interventions are promising for educating adolescents about sleep. Future programs should translate increased motivation into long-term behavioral change. The identification of barriers and support to assist this change is recommended.