Purpose: The aim of this study was to identify the correlation between spiritual well-being and mental health and to examine the effect of spiritual well-being on mental health in nursing students. Methods: Between October 2011 and November 2012 nursing students (n=193) in 2 universities in 2 cities completed measures of spiritual well-being and mental health. Data were collected using questionnaires and analyzed using descriptive statistics, t-test, ANOVA, Pearson correlation coefficient, and multiple regression with the SPSS/Win 20.0 program. Results: All variables correlated significantly with each other in the positive direction: mental health was correlated with existential well-being (r=.72) and religious spiritual well-being (r=.23). The factor influencing mental health was existential well-being (β=.70, p<.001). Existential well-being explained 51.0% of nursing students`` mental health. Conclusion: The results of the study indicate that spiritual well-being of nursing students is related to mental health. Especially, existential well-being has a major effect on mental health in nursing students. Therefore, it is necessary to develop strategies which strengthen existential well-being in order to improve perspective nursing students.