This study was a clinical trial with aim of determining the impact of professional ethics education based on case-based and lecture-based learning on moral sensitivity and ethical reasoning of nursing students in the school of Urmia nursing and midwifery. All nursing students at semester 7 and 8, who had been recruited for this study, were divided into two groups. 36 students in the intervention group (case-based learning) and 34 students in the control group (lecture-based learning) were assigned. Main inclusion criteria: no history of participating in ethical seminars.Main exclusion criteria: absence of more than two sessions. Before the intervention, both groups were examined by using two questionnaires; moral sensitivity and ethical reasoning (nursing dilemma test) questionnaires. Contents of training in this study, were the same for both groups, the only difference was the methods of teaching. Intervention group (in 8 sessions) and control group (in 4 sessions) were trained with case-based and lecture-based learning methods about nursing ethics and related scenarios (birth defects, mandatory prescription drug, medication error, new nurse training, applying for end of life, end of life care) respectively. One month after finishing intervention, all students who participated in the study, using the previous questionnaire, were evaluated.