BACKGROUND: Childhood trauma is a pervasive issue contributing to adverse mental health outcomes. Obtaining optimal sleep supports healthy development and protects against mood-related disorders. Whether sleep serves as a potential buffer between trauma and adverse mental health outcomes holds promise for informing targeted interventions and prevention for adolescents. METHODS: Data were drawn from the baseline assessment of a randomised controlled trial of a mental health prevention program. A total sample of 752 adolescents completed an online, self-report survey in 2023. Participants were students (M RESULTS: The majority of participants (82%) reported exposure to at least one traumatic event. The mean number of traumatic events was 1.8. Trauma was independently associated with higher depressive and anxiety symptoms and lower mental wellbeing scores. Those reporting exposure to one or more traumatic events were more likely to report difficulties falling asleep and less likely to report meeting nightly sleep duration guidelines. We found a significant interaction between meeting nightly sleep duration guidelines and any trauma exposure on depressive and anxiety scores, such that depression and anxiety symptoms were lower in trauma-exposed adolescents who met sleep duration guidelines compared to those who did not meet sleep guidelines. CONCLUSIONS: Obtaining optimal amounts of sleep each night may help mitigate anxiety and depressive symptoms for non-clinical adolescents exposed to trauma, however, longitudinal research is needed to confirm the directionality of the relationships between trauma, sleep, and mental health symptoms. Future research should examine the effectiveness of public health interventions targeting sleep behaviours in adolescents to promote mental wellbeing.