Purpose: This study was conducted to identify the effects of life stress and depression in undergraduates on suicidal ideation. Methods: The participants in this study were 306 nursing students from three different cities. Collected data were analyzed using t-test, ANOVA, Pearson correlation coefficients, and stepwise multiple regression. Results: The mean score for life stress was 48.48, for depression, 28.59, and for suicidal ideation, 5.90. There were positive relationships between depression and life stress, suicidal ideation and life stress, and suicidal ideation and depression. The four factors of life stress, depression, school life, and gender were identified as factors influencing on suicidal ideation in undergraduates. Conclusion: The findings of this study indicate that the establishment of mental health care centers in universities, and development and implementation of nursing intervention programs for suicide prevention would be helpful.