Purpose: This aim of this study was to investigate the mediating effect of interpersonal relations on the association between emotional intelligence and happiness of nursing students. Methods: Both junior and senior nursing students were selected for this study (N=187). The survey was conducted using self-reported questionnaire between March and May, 2018. The data were analyzed using descriptive statistics, independent t-tests, one-way ANOVA, Pearson’s correlation coefficients, and multiple linear regression analysis with Sobel test. Results: The happiness of nursing students had positive correlation with emotional intelligence (r=.70, p<.01) and interpersonal relations (r=.60, p<.01). Emotional intelligence had positive correlation with interpersonal relations (r=.63, p<.01). Interpersonal relations had a partially mediating effect on the relationship between emotional intelligence and happiness of nursing students. Conclusion: According to this study, interpersonal relations played an important role to buffer the impact of emotional intelligence on happiness among nursing students. Therefore, it is necessary to develop a psychological program to improve interpersonal relations to enhance the happiness of nursing students.