摘要Background Researches on the mental health of Korean adolescents during COVID-19 have largely focused on those from monocultural families,but there is limited data on sadness,suicidal ideation,and suicide attempts in multicultural adolescents.Methods This nationwide serial cross-sectional study included 688,708 adolescents aged 12-18 years who participated in the Korean Youth Risk Behavior Web-based Survey from 2011 to 2022.We compared and analyzed the prevalence of sad-ness,suicidal ideation,and suicide attempts among multicultural and monocultural adolescents.Multicultural adolescents were defined as those with at least one non-Korean parent.Results In 2021,the prevalence of sadness among multicultural adolescents was 31.86％[95％confidence interval(CI)30.00-33.71],suicidal ideation 17.17％(15.74-18.61),and suicide attempts 4.25％(3.51-4.99).Among monocultural ado-lescents,the prevalence rates were 26.09％(25.50-26.69)for sadness,12.41％(11.97-12.85)for suicidal ideation,and 1.92％(1.76-2.67)for suicide attempts.Adolescents from multicultural backgrounds were found to have higher rates of sadness,suicidal ideation,and suicide attempts.In the general population,these rates had decreased during the pre-pandemic period but increased after the onset of the pandemic then stabilized from 2020 to 2021.Female gender,smoking,alcohol use,and low school performance emerged as significant risk factors.However,no distinct risk factors specifically linked to suicide attempts were identified.Joinpoint regression analysis results aligned with the beta slope values in the main findings,reflect-ing a consistent pattern across both analyses.Conclusions This study revealed that sadness,suicidal ideation,and suicide attempts increased during the pandemic,revers-ing a pre-pandemic decline.Multicultural adolescents faced these issues more than monocultural ones,underlining the need for targeted public health measures to support at-risk adolescents during pandemics.