BACKGROUND : Suicide is the ninth leading cause of death in adolescents aged 15-19 years in Taiwan. Suicidal ideation is an important predictor of committing suicide among adolescents. OBJECTIVE : The aim of this study was to examine the important risk factors, the protective factors, and the role of protective factors on the relationship of risk factors to suicidal ideation among Taiwanese adolescents aged 15-19 years. METHODS : By adopting a cross-sectional study, senior high school students (n = 577) aged 15-19 years in southern Taiwan were recruited for this study. An anonymous self-reported questionnaire was used to collect demographic characteristics, risk factors, protective factors, and suicidal ideation of the sample. Hierarchical logistic regression was used to identify the important risk and protective factors and the interaction between risk and protective factors on suicidal ideation. RESULTS : Nearly 18% (n = 101) of the participants reported having suicidal ideation during the past 12 months. Gender (female; odds ratio [OR] = 4.23), life stress (OR = 1.03), depression (OR = 3.44), peer suicidal ideation (OR = 4.15), and bullying victimization (OR = 1.81) were important risk factors of suicidal ideation among the targeted sample. In addition, self-esteem (OR = 0.92) and emotional adaptation (OR = 0.88) were important protective factors of suicidal ideation. Self-esteem and emotional adaptation were not used to moderate the negative effects of life stress, depression, perceived peer suicidal ideation, and bullying victimization on suicidal ideation. The final model explained 40.6% of the total variance in suicidal ideation and correctly predicted 86.1% of participants with suicidal ideation. CONCLUSIONS : Suicidal ideation prevention programs should be targeted to female adolescents. School-based efforts that provide adolescents with self-esteem enhancement, emotional regulation skills training, positive peer norms for life, coping skills for managing stress and depression, and antibullying programs might help reduce the suicidal ideation of adolescents.