Neonatal intensive care unit (NICU) nurses are often faced with complex clinical and ethical problems. Little is known about the role of the NICU nurse in ethical decision-making, or processes that inform decision-making in this setting. The purpose of this study was to explore and describe nurses’ perceptions of their role as patient advocate, clinical situations that cause them concern and the extent of their involvement in ethical decision-making. A combined quantitative and qualitative research design was used. A questionnaire was administered to nurses working in the NICU of the sole perinatal tertiary referral centre of Western Australia, Australia. Findings showed that NICU nurses saw their role in ethical decision-making primarily as advocating for the best interests of the infant and family, that they used clinical knowledge and experience to guide ethical decision-making, they were able to clearly articulate ethical problems and respond to them according to the clinical scenario and, while being primarily assertive in presenting their views, some nurses took a more passive approach. These findings support the need for development of a multidisciplinary model for ethical decision-making, where the view of all team members are considered.