Background: Previous research suggests that, to design a program to help students to develop ethical decision making, competence and courage to confront ethical dilemmas should be critical components. Purpose: This study examines the effect of an ethical decision-making reasoning scheme in ethical decision making and communication self-efficacy in nursing students. Methods: This study was a prospective and randomized, open-label, controlled trial design. Nursing students from a medical university served as participants. Students were randomly assigned to an intervention group (IG), which received the ethical decision-making reasoning scheme intervention, or a control group (CG), which received a standard general course. The effect was measured with the Ethical Decision-Making Scale-Revised and the Self-efficacy for Communication Scale. Analysis of covariance (ANCOVA) was used to measure between group differences, and paired t-tests were used to measure pre-and post-IG/CG differences. Results: A total of 101 nursing students were included and randomly assigned to the IG (n = 50) and CG (n = 51), and 41 IG and 43 CG students completed all aspects of the study. The findings show that there was significant improvement in self-efficacy in communication (t = 2.341, p = .024) and a decrease in difficulty in communication (t = 2.330, p = .025) in the IG. Ethical decision-making competencies improved more in the IG compared to the CG (F = 4.856, p = .034). Ethical decision-making competencies increased in both males and females, but there were no significant differences between males and females at the end of study (F = 0.264, p = .610). Conclusion: These findings suggest that ethical decision-making training can improve students' confidence in communicating with patients and may help to improve students' more complex ethical decision making.