Climate change is causing a range of impacts on communities such as more frequent extreme weather, air pollution, changing distribution of infectious diseases, mental health impacts and others. The 2018 report of the Lancet Countdown on health and climate change concluded that “…climate change is the biggest global health threat of the 21st century” (Watts et al. 2018). This study aims to provide a quantitative supply-chain assessment of the environmental impacts of the health system in Australia's largest state, New South Wales (NSW). We integrate a range of environmental indicators, such as greenhouse gas emissions (GHGEs), water use and waste into a cloud-computing platform for constructing a custom-built sub-national multi-regional input-output (MRIO) table for Australia. We then use specific health system data to construct a hybrid life-cycle assessment model featuring detail on the health system, and quantify the environmental impact of interactions of the health system with the rest of the NSW and Australian economy. Our findings show that the health system in Australia's largest state was responsible for 6.6% of the total estimated GHGEs in 2017, 4% of water use, and 8% of waste produced in the NSW economy. The results highlight the need for implementation of targeted policies to reduce not only the direct environmental impacts generated by health systems but also those from its supply chains that connect with many other economic sectors.