Study objectivesStressful ethnic/racial experiences, such as peer ethnic/racial victimization, may harm adolescents’ adjustment. Using a daily diary design, the current study examined how same-night and previous-night sleep may moderate the within-person associations between peer ethnic/racial victimization and school engagement. MethodsThe analytic sample consisted of 133 ninth graders (Mage = 14.54 years old; 44% Black, 21% White, 16% Latinx, 5% Native, 4% Asian, and 9% other). Adolescents reported their peer ethnic/racial victimization experiences and school engagement every day for 14 consecutive days. Sleep was measured objectively by actigraphy watches daily during the 14 days. ResultsMultilevel analyses identified significant interactions between peer ethnic/racial victimization and same-night time in bed and latency for next-day engagement. The negative association between victimization and next-day school engagement was only significant when adolescents had shorter time in bed and longer latency than their typical levels that night, supporting the recovery role of sleep (ie, same-night sleep helps adolescents recover from victimization). There was also a significant interaction between previous-night time in bed and today's peer ethnic/racial victimization for same-day school engagement. The negative association between victimization and same-day school engagement was only significant when adolescents had shorter time in bed than their typical levels the previous night, supporting a preparatory hypothesis of sleep (ie, sleep helps prepare adolescents for next-day victimization). Neither previous-night nor same-night sleep efficiency moderated the association between victimization and school engagement. ConclusionsFindings highlighted sleep as an important bioregulatory protective factor that may alleviate the challenges associated with ethnic/racial victimization.