Background <p>The COVID-19 pandemic has had a serious impact on people’s mental health and increased the risk of suicide. Research on suicidal ideation in adolescents is needed, especially since suicide is one of the leading causes of death among adolescents.</p> Methods <p>Suicidal ideation among late adolescents was analyzed using data from the 2021 Korea Community Health Survey (KCHS). The subjects of the study were 12,828 late adolescents aged 19 to 24 years. The Chi-squared test and multivariable logistic regression were used to investigate the impact of sociodemographic characteristics, health-behavioral factors, and factors related to COVID-19 on suicidal ideation. Finally, the analysis used an adjusted odds ratio with a 95% confidence interval.</p> Results <p>It was found that 5.4%of the study subjects experienced suicidal ideation. The ideations were higher in women than in men. Those who graduated from college or higher, had an income of more than 2&#xa0;million won, and lived in rural areas had lower levels of suicidal ideation than those who did not. Suicidal ideation was also influenced by smoking, and the physical activity of the subjects. When the impact of COVID-19 variables was examined, the group who believed they were at a high risk of infection had 0.68 times the suicidal ideations of adolescents who did not. Also, adolescents who experienced a severe economic loss due to COVID-19 were 1.89 times more likely to have suicidal ideation than others who had not suffered such losses.</p> Conclusion <p>The results of this study suggest that suicidal ideations in late adolescents are influenced by socioeconomic characteristics, health behavioral factors, and factors related to COVID-19. These results can be used as basic data when developing youth mental health promotion programs.</p>