We aimed to analyze the trends and associations between the oral and mental health of Korean adolescents using the Korea Youth Risk Behavior Web-based Surveys. In total, 713,713 adolescents who participated in the surveys were included. To examine trends in oral and mental health, Pearson’s correlation coefficients were calculated between the weighted percentages and years, and the regression line slope was assessed to estimate annual changes. A complex sample logistic regression analysis was also performed. Experiencing oral symptoms and suicide-related factors both showed a gradually decreasing trend from 2008 and slight increases in 2017 and 2016, respectively. Compared with adolescents who had no oral symptoms, those with all six oral symptoms showed an increase in suicide attempts in the last 12 months, suicide ideation, and feelings of sadness and despair. In conclusion, experiencing more oral symptoms is associated with an increased risk of suicide-related factors.