Background: Moral reasoning is a vital skill in the nursing profession. Teaching moral reasoning to students is necessary toward promoting nursing ethics. Objectives: The aim of this study was to compare the effectiveness of problem-based learning and lecture-based methods in ethics education in improving moral decision-making, moral reasoning, moral development, and practical reasoning among nursing students. Research design: This is a repeated measurement quasi-experimental study. Participants and research context: The participants were nursing students in a University of Medical Sciences in (...) west of Iran who were randomly assigned to the lecture-based or the problem-based learning groups. The subjects were provided nursing ethics education in four 2-h sessions. The educational content was similar, but the training methods were different. The subjects completed the Nursing Dilemma Test before, immediately after, and 1 month after the training. The data were analyzed and compared using the SPSS-16 software. Ethical considerations: The program was explained to the students, all of whom signed an informed consent form at the baseline. Findings: The two groups were similar in personal characteristics. A significant improvement was observed in the mean scores on moral development in the problem-based learning compared with the lecture-based group. Although the mean scores on moral reasoning improved in both the problem-based learning and the lecture-based groups immediately after the training and 1 month later, the change was significant only in the problem-based learning group. The mean scores on moral decision-making, practical considerations, and familiarity with dilemmas were relatively similar for the two groups. Conclusion: The use of the problem-based learning method in ethics education enhances moral development among nursing students. However, further studies are needed to determine whether such method improves moral decision-making, moral reasoning, practical considerations, and familiarity with the ethical issues among nursing students. (shrink)