PURPOSE: The purpose of this study was to identify the effects of the action learning approach on the self-confidence and knowledge of health assessment, critical thinking ability and class satisfaction in students taking health assessment courses. METHODS: This non-equivalent control group pretest-posttest study enrolled 127 nursing students as participants, with 64 and 63 in the experimental and control group, respectively. These two groups attended 33 hours (2 or 4 hours per week for 11 weeks) of action learning and traditional classes, respectively. Differences in the dependent variables between the two groups were compared before and after the intervention using independent t-test. RESULTS: The action learning group reported significantly greater self-confidence in health assessment (t=5.10, p < .001) and critical thinking ability (t=2.23, p=.027) than the control group. There was no significant difference in knowledge of health assessment or class satisfaction between two groups (p>.05). CONCLUSION: These findings indicate that action learning is an effective intervention for enhancing self-confidence and critical thinking ability in nursing education.