To investigate ED and intensive care unit healthcare professionals' perspectives and knowledge of the law that underpins end-of-life decision-making in Queensland, Australia. An online survey with questions about perspectives, perceived, and actual, knowledge of the law was distributed by the professional organisations of medical practitioners, nurses and social workers who work in Queensland EDs and intensive care units. The survey responses of 126 healthcare professionals were included in the final analysis. Most respondents agreed that the law was relevant to end-of-life decision-making, but that clinician and family consensus mattered more than following the law. Generally, doctors' legal knowledge was higher than nurses'; however, there were significant gaps in the knowledge of all respondents about the operation of advance health directives in Queensland. The legal framework that supports end-of-life decision-making for adults who lack decision-making capacity has been in place for more than two decades. Despite frequently being involved in making or enacting these decisions, gaps in the legal knowledge of healthcare professionals who work in EDs and intensive care units in Queensland are evident. Further research to better understand how to improve knowledge and application of the law is warranted.