Background & objectives: Patient safety is a crucial factor in the provision of quality healthcare and is therefore a global health concern. It is an area in which ethical concerns and high-quality clinical practice are inextricably linked. This study investigates the effect of education around ethical principles on nurses' perception of patient safety in a psychiatric unit. Materials & methods: This pre-and post-test descriptive study was conducted in a mental health inpatient unit in a hospital in Tehran, capital of Iran, in 2018. A total of 33 nurses, selected by census sampling, participated in the study. Data was collected using a demographics questionnaire and Hospital Survey on Patient Safety Culture (HSOPSC), and was analyzed with SPSS21. Results: The mean score of patient safety was 116.85 ± 9.98 before the educational intervention, 143.58 ± 7.21 immediately after intervention, and 153.12 ± 9.47 1 month after intervention. The rate of error report by most participants over the past 12 months was 3-5 and 6-10 events before intervention, and 6-10 events immediately after and 1 month after intervention. Also, 42.4% of the participants assessed patient safety after intervention as very good and 36.4% assessed it as acceptable and very good 1 month after intervention whereas most of the participants (45.5%) assessed patient safety as acceptable before intervention. Conclusion: Education on ethical principles exerts a positive effect on nurses' perception of patient safety culture. Thus, it is recommended as an effective method of promoting nurses' perception of this variable. In this way, healthcare quality and enhanced patient safety can be achieved.