The transport sector is responsible for a large and growing share of global emissions that affect climate change. Bus Rapid Transit (BRT) systems have been identified as an efficient public transport option, but their total emissions across the entire operation chain have not been quantified. This paper proposed a carbon footprint model of the BRTsystem based on a life cycle assessment (LCA) approach, with three components: infrastructures, fuels and vehicles. A case study of Xiamen City was carried out to offer a broader perspective on the greenhouse gas (GHG) impact. Results showed that the total carbon footprint of Xiamen’s BRT system was 55,927 t CO2e per year. The main emission phases, infrastructure operations, vehicle fuel consumption and infrastructure material production, respectively, accounted for 31%, 30% and 23%. The direct emission from fuel consumption was 13,059 t CO2e per year, accounting for 23% of the total carbon footprint. Considering only direct emissions, the BRTsystem could achieve reductions of approximately 25,255 t CO2e per year compared to the no-build option. The carbon footprint model proved effective in identifying and measuring GHG emissions of each activity of the BRT life cycle.