Protection of human rights of individuals with mental illness is basic to ethical and legal psychiatric care. Nurses play an important role in safeguarding these rights in mental healthcare settings; and this depends largely on the nurses’ knowledge, attitudes, and clinical practices. Therefore, this study aimed to assess the knowledge, attitude, and practice of psychiatric nurses regarding the human rights of individuals with mental illness and to examine the relationships among these variables. A quantitative descriptive correlational design was adopted. Data collected from a total of 109 psychiatric nurses working in the inpatient department of a selected psychiatric hospital in Saudi Arabia; through a self-administered questionnaire via Google Forms link. The majority of participants (64%) had good knowledge, while 33% showed moderate knowledge. The mean attitude score was 50.94 ± 6.20, indicating a moderately favorable attitude; however, 70% of nurses demonstrated a neutral attitude. The mean practice score was 24.72 ± 8.28, reflecting a moderate level of rights-based practice, with 33% exhibiting poor practice. A very strong positive correlation found between knowledge and attitude (r = 0.928, p < 0.001) and between knowledge and practice (r = 0.946, p < 0.001) and a moderate positive correlation between attitude and practice (r = 0.506, p < 0.001). This indicates though psychiatric nurses had good knowledge and favorable attitudes toward human rights, practice remains suboptimal. Hence strengthening formal training is essential to bridge the gap between knowledge and practice to promote ethical psychiatric care.