BACKGROUND A significant number of Korean adolescents have suicidal ideations and it is more prevalent among adolescents than any other age group in Korea. OBJECTIVE This study was conducted to attain a better understanding of the contributing factors to suicidal ideation among Korean adolescents. METHODS We recruited 569 high school students in Grades 10 and 11 in Pyeongtaek, Korea. The Beck Scale for Suicidal Ideation was used to measure suicidal ideation as the outcome variable. The Interpersonal Needs Questionnaire, the Beck Hopelessness Scale, the School Related Stress Scale, the Olweus Bully/Victim Questionnaire, and the Youth Risk Behavior Surveillance questions were used to measure thwarted belongingness and perceived burdensomeness, hopelessness, school-related stress, bullying, and previous suicidal behaviors, respectively. Data analyses included descriptive statistics and structural equation modeling. RESULTS The findings suggest that perceived burdensomeness, hopelessness, school-related stress, and previous suicidal behaviors have significant direct effects on suicidal ideation. Hopelessness fully mediated the relation between thwarted belongingness and suicidal ideation, and partially mediated between perceived burdensomeness, school-related stress, and suicidal ideation. CONCLUSIONS These findings provide more specific directions for a multidimensional suicide prevention program in order to be successful in reducing suicide rates among Korean adolescents.