The purpose of this study was to explore significant variables predicting adolescent suicidal attempts. Socio-environmental variables such as gender, school record, school grade, school adaptation, and family intimacy together with intra-individual variables including depression, anxiety, delinquency, stress, and self-esteem were considered as candidates. Data from 1481 adolescents were collected from Korea National Youth Policy Institute. For statistical analyses, hierarchical logistic regression analysis was performed. Results of hierarchical logistic regression analysis showed that gender, school grade, depression, delinquent, stress, and family intimacy were significant predictors of suicidal attempts of adolescents. Among those, the most powerful predictor was depression, and the second was delinquency. Classification accuracy by the model of our study was 87.6%. Implications and limitations of present study and suggestions for future study were discussed.