Objective This study was performed to identify factors associated with depression and anxiety among Korean adolescents during the coronavirus disease (COVID-19) pandemic.Methods We conducted a cross-sectional study of 1,898 Korean adolescents (55.2% male, 44.8% female) ranging in age from 12 to 17 years (mean±standard deviaion age, 15.4±2.6 years). Depression and anxiety were defined as a Patient Health Questionnaire-9 score ≥10 and Generalized Anxiety Disorder-7 score ≥10, respectively. Other questionnaires included sociodemographic data, psychosocial stresses, and experiences in association with COVID-19. Psychiatric scales included Gratitude Questionnaire-6, Perceived Stress Scale-10, and UCLA Loneliness Scale-3.Results The prevalence rates of depressive and anxiety symptoms among participants were 13.8% and 21.0%, respectively. Multivariable logistic regression analysis revealed that female sex, fear of COVID-19 infection, low gratitude were risk factors for depression. Fear of COVID-19 infection, increased TV watching time, and academic-related stress were risk factors for anxiety.Conclusion Depression and anxiety were prevalent during the pandemic in Korean adolescents, and were associated with fear of COVID-19 infection. Providing appropriate information on COVID-19, helping adolescents manage academic-related stress and maintain daily life patterns, and implementing interventions to foster gratitude are important for preventing depression and anxiety in Korean adolescents.