Nurses’ ethical choices and behavior strongly influence the quality of care they provide. Strengthening moral reasoning is therefore essential for improving ethical decision-making in clinical practice. This study aimed to evaluate and compare the effects of ethics training delivered through lectures versus group discussions on nurses’ moral reasoning, moral distress, and moral sensitivity. In this randomized clinical trial with a pre- and post-test design, 66 nurses with below-average moral reasoning scores were randomly divided into three groups (n = 22 each): two intervention groups and one control group. The interventions included ethics training via lectures or group discussions, while the control group received no instruction. Participants completed a sociodemographic survey, the Nursing Dilemma Test (NDT), the Moral Distress Scale (MDS), and the Moral Sensitivity Questionnaire (MSQ). Data were analyzed using both unadjusted and adjusted binary logistic regression, with results expressed as odds ratios (OR) and 95% confidence intervals (CI). Adjusted analyses indicated that discussion-based training led to greater improvements in nursing principle thinking (NPT) scores compared to lecture-based training (OR: 13.078, 95% CI: 3.238–15.954, P = 0.008). Both lecture and discussion groups achieved significantly higher NPT scores than the control group (lecture: OR: 14.329, 95% CI: 2.005–16.171, P < 0.001; discussion: OR: 18.01, 95% CI: 5.834–22.15, P < 0.001). Moral sensitivity increased more after discussion sessions than lectures (OR: 10.874, 95% CI: 6.043–12.886, P = 0.005) and the control group (OR: 13.077, 95% CI: 8.454–16.774, P = 0.002). Both training methods reduced moral distress compared to control, with no significant difference between them (lecture: OR: 0.105, 95% CI: 0.015–0.717, P = 0.021; discussion: OR: 0.089, 95% CI: 0.015–0.547, P = 0.009). Ethics training enhances nurses’ moral reasoning, and group discussions further improve moral sensitivity. These findings support incorporating ethics workshops into professional nursing education and student curricula to strengthen ethical practice. Iranian Registry of Clinical Trials (IRCT2015122116163N5), 02/07/2016.
