Objectives: This study aimed to confirm the association between self-determination and self-directed learning among Korean nursing students, as well as the mediating effect of academic self-efficacy. Methods: Data from 139 nurse students were surveyed in this descriptive cross-sectional study. They were collected from Oct 1 to 30, 2020, using self-report questionnaires. The collected data were analyzed using descriptive statistics, independent t-test, one-way analysis of variance, Scheffé test, Pearson's correlation coefficient analysis, and mediated model for PROCESS macro using the SPSS/WIN 24.0. Results: Self-directed learning was positively associated with self-determination (r=.56, p<.001) and academic self-efficacy (r=.63, p<.001). Furthermore, academic self-efficacy had a mediating effect on the relationship between self-determination and self-directed learning (B=0.21, 95% CI=0.12~0.32). Conclusion: The impact of self-determination on the self-directed learning among nursing students was mediated by academic self-efficacy. Therefore, these results provide important data for future self-directed learning in nursing education.