Background: Nurses who work in psychiatry settings encounter important ethical and legal challenges in practice and caring for patients with mental disorders. This study was aimed to determine barriers of applying the ethical and legal issues in psychiatric nursing and its relation to staff nurses' knowledge. Methods: Descriptive design was used in this study. Purposive sample of 120 psychiatric nurses at Beni-Suef and Benha Mental Health Hospital was recruited for this study. A structured questionnaire developed by researchers was used for data collection. Results: Revealed that the majority (80.0%) of the subjects had unsatisfactory knowledge regarding the legal aspects. There is a highly positive statistically significant relationship between legal knowledge and ethical practices among participating psychiatric nurses (r=0.289, p < 0.000). Conclusion: The results showed that, the barriers most frequently observed by the nurses who work in psychiatric hospitals are lack of time, the frequent number of patients with fewer nurses the community's perception of inferiority towards nursing profession, and lack of authority to make decisions. There is a negative statistically significant relationship between ethical practices and barriers among participating psychiatric nurses. Recommendations: Develop nursing education programs that are specifically focused on ethical problems in the fields of mental health and psychiatry to increase their awareness regarding ethics-legal aspects.