Purpose: This study aimed to measure the level of patient advocacy (the core attribute), nursing professionalism and ethical climate perceived by hospital nurses in Korea, and to identify factors influencing patient advocacy (the core attribute). Method: This study was conducted on 234 full-time nurses who had been working for more than 1 year at a general hospital located in a provincial city in Korea. Data were collected from November 15 to 30, 2024, using questionnaires. The collected data were analyzed using IBM SPSS/WIN 27.0. Results: Among patient advocacy, ‘safeguarding patients’ autonomy’ was explained by 30.0% by professional self-concept, patients, and professional identity in nursing, ‘acting on behalf of patients’ was explained by 34.0% by professional self-concept, role of nursing practice, patients, originality of nursing, and professional identity in nursing, and ‘championing social justice’ was explained by 36.0% by professional self-concept, patients, and managers. Conclusion: In order to improve patient advocacy of hospital nurses, it could be concluded that improving professional self-concept among the sub-factors of nursing professionalism and improving patients among the sub-factors of ethical climate are very effective. Therefore, nursing managers need to make managerial efforts to improve nurses’ professional self-concept and awareness of patients.