Objective To develop and preliminarily evaluate the effectiveness of an ethical sensitivity training program for undergraduate nursing students. Methods An ethical sensitivity training program was developed based on literature review and two rounds of Delphi expert consultation. Then 41 undergraduate nursing students were recruited using convenience sampling and randomly assigned to either a control group (n=21) receiving the routine curriculum or an intervention group (n=20) receiving the routine curriculum plus a 12-session ethical sensitivity training. Participants′ ethical sensitivity was assessed using the Ethical Sensitivity Questionnaire for Nursing Students at three time points:pre-intervention, post-intervention, and one-month follow-up. Results Significant main effects of group and time, as well as a significant group-by-time interaction effect, were observed for the total ethical sensitivity score and the scores on the dimensions of respect for individuals, reasonable care, and maintaining patients′ confidentiality (all P<0.05). Conclusion The ethical sensitivity training program is scientifically grounded, feasible, and effective in enhancing ethical sensitivity among undergraduate nursing students.