Developing countries, including Brazil, Russia, India, China and South Africa (BRICS), are implementing mitigation strategies for greenhouse gas (GHG) emissions in specific sectors, such as municipal solid wastes (MSW), to reduce the impacts of climate change. The purpose of this research was to evaluate different GHG emission mitigation scenarios in MSW management in Brazil, countrywide and at municipal level, to determine the best transition towards eco-efficiency (TEE) relative to the current scenario. Environmental (GHG emissions, using the CO2ZW tool) and economic (operating and investment costs and climate change externalities) indicators were determined and analysed per ton of MSW treated, based on field work and national data. An analysis was made of six scenarios of transitions of MSW management and treatment via wet processes (composting and mechanical biological treatment – MBT), dry routes (recycling and incineration) and disposal in sanitary landfills (DSL). The most eco-efficient scenario for Brazil and the municipalities with the largest populations, such as São Paulo and Sorocaba, corresponded to: 70% composting and 30% DSL for wet MSW and; 70% recycling and 30% DSL for dry MSW. In the smaller municipalities such as Humaitá, Piedade and Santa Cruz do Sul, the best results in TEE were: 42% composting and 58% DSL for wet MSW and; 41% recycling and 59% DSL for dry MSW. The scenarios showing the lowest TEE performance were MBT and incineration, due to the high costs of these technologies in Brazil.