Although highly efficient, the Swiss healthcare system accounts for 6.7% of the country's greenhouse gas emissions. In Geneva, our study assessed its carbon footprint for the first time, estimating it at 436,831 tCO2e in 2022. Hospitals (47%) and medications (58.6%) are the main factors and sources of these emissions. Various scenarios, including health promotion and prevention, underscore the importance of direct and indirect measures to cut these emissions by 70% by 2040. These approaches are adaptable to other cantonal healthcare systems.