This cross-sectional study among nurses at the hospitals of the Tehran University of Medical Sciences aimed to investigate the extent of involvement in patient advocacy practice among nurses. Participants (n=330) were selected using proportionate systematic random sampling. Data were gathered through patient advocacy questionnaires and analysed using descriptive/inferential statistics. The average of nurses' patient advocacy practice was 3.848+ 0.304 (possible range 1-5). One third of the participant nurses had high scores in practising patient advocacy, two thirds of them had scores in the medium range and 0.6% of nurses had low scores. The majority of nurses (83.5%) declared their commitment to patient advocacy as high, and 42.5% believed they had enough ability to practise advocacy. Half of the participants claimed to have faced problems following advocacy practices. The problems that most participants reported included conflict with colleagues and/or superiors, receiving oral/written admonitions, and shift and/or ward changes. Patient advocacy scores were significantly higher among female nurses, head nurses, and those who had more commitment and ability for patient advocacy (p<0.001). In contrast, nurses who worked in more than one hospital simultaneously due to financial need (p=0.048), and experienced conflict with superiors (p=0.047) scored less than others. The nurses in our study carried out advocacy at acceptable levels and adopted it as part of their own professional role. Nurses tended to advocate for patients, but they faced many challenges in this.