Objective: Despite growing evidence of disparities in sleep quality between sexual minoritized and heterosexual youth, the reasons for these disparities are not well understood. LGBQ+ adolescents often experience challenging peer relationships, which could negatively impact their sleep quality. The current study examined the prospective relationship between sexual minority status and sleep quality over 12 months and evaluated whether peer victimization and social support at 6 months mediated this relationship among adolescents. Methods: This study involved a secondary analysis of data from a community sample of 800 adolescents (57.5% female; M-age = 14.42 years, SD = 0.83). Data were collected using web-based surveys over 12 months with three time-points: baseline, 6-, and 12-month. Results: Approximately 19.4% of adolescents self-identified as LGBQ+. Compared to heterosexual adolescents, LGBQ+ adolescents reported poorer global sleep quality, lower perceived social support, greater peer victimization, childhood victimization, and were more likely to be female (all ps < .001). In a longitudinal, parallel mediation analysis adjusting for baseline age, gender, global sleep quality, and childhood victimization, LGBQ+ adolescents reported higher rates of peer victimization (b = 0.262 [0.049], p < .001) and less social support (b = - 0.385 [0.146], p = .008) at 6 months compared with heterosexual peers, predicting poor global sleep quality (b = 0.495 [0.191], p = .010 for peer victimization and b = - 0.161 [0.068], p = .018 for social support) at 12 months. Conclusion: These findings highlight that sexual minority adolescents face increased risks of peer victimization and reduced social support from peers, which contribute to poorer sleep quality. The findings may guide the development of adolescent sleep interventions that also improve social health and relationships. (c) 2024 National Sleep Foundation. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.