This study is a descriptive study aimed to assess nurses' knowledge; Experience toward psychiatric this study is a descriptive study aimed to assess nurses' knowledge, Experience toward psychiatric patient's advocacy, the study was conducted at psychiatric departments at El-Abassia Mental Health Hospital in Cairo. Sampling was a purposive sample of 70 nurses from 600 nurses who are working in the previously mentioned settings. Data were collected using 1) interviewing sheet containing (a)Socio-demographic sheet for personal characteristics and (b) questionnaire sheet about nurses' knowledge toward psychiatric patient's advocacy and 2) observation checklist to assess nurses' experience toward psychiatric patient's advocacy. The present study revealed that the majority nurses were females. More than one third among nurses were more than 10 years of experience. Half of nurses were had training courses about psychiatric patients' rights. While more than three quarter were had low knowledge about psychiatric patient's rights. Less than three quarter were had low knowledge about psychiatric patient's advocacy. Less than two thirds were had low experience about psychiatric patient's advocacy. A positive relation between nurses' knowledge and experience toward psychiatric patient advocacy. The study recommended that develop an in-service training program for mental health nurses on knowledge about the nurse's advocacy of the psychiatric patient, Nurses need more support from supervisors and may need to add education in this area to the curriculum of trainees in psychiatric nursing, Raising the awareness of nursing staff about the importance of psychiatric patient's advocacy and rights granted to the nurse,Furthermore, Support nursing from the medical team and provide opportunities and resources that facilitate the process of psychiatric patient's advocacy, And the role of the nurse as advocate of psychiatric patient's rights should be highlighted in the curriculum.