question: OBJECTIVE: To assess the prevalence and sociodemographic correlates of insomnia symptoms among Chinese adolescents and young adults affected by the outbreak of coronavirus disease-2019 (COVID-19). METHODS: This cross-sectional study included Chinese adolescents and young adults 12-29 years of age during part of the COVID-19 epidemic period. An online survey was used to collect demographic data, and to assess recognition of COVID-19, insomnia, depression, and anxiety symptoms using the Pittsburgh Sleep Quality Index (PSQI), the Patient Health Questionnaire (PHQ-9), and the Generalized Anxiety Disorder (GAD-7) questionnaires, respectively. The Social Support Rate Scale was used to assess social support. RESULTS: Among 11,835 adolescents and young adults included in the study, the prevalence of insomnia symptoms during part of the COVID-19 epidemic period was 23.2%. Binomial logistic regression analysis revealed that female sex and residing in the city were greater risk factors for insomnia symptoms. Depression or anxiety were risk factors for insomnia symptoms; however, social support, both subjective and objective, was protective factors against insomnia symptoms. Furthermore, anxiety and depression symptoms were mediators of social support and insomnia symptoms. CONCLUSIONS: Results of this study revealed a high prevalence of sleep problems among adolescents and young adults during the COVID-19 epidemic, especially senior high school and college students, which were negatively associated with students' projections of trends in COVID-19. The adverse impact of COVID-19 was a risk factor for insomnia symptoms; as such, the government must devote more attention to sleep disorders in this patient population while combating COVID-19.