The objective of this paper is to derive, for the first time, decarbonization roadmaps for the ten nations of ASEAN. This study first presents a regional view of ASEAN’s fossil and renewable energy usage and energy-related CO2 emission. Results show that renewable energies have been losing ground to fossil energies in the last two decades and fossil fuels will likely continue to be an important part of ASEAN’s energy mix for the next few decades. Therefore, decarbonizing efforts should focus not only on increasing the share of renewable energies in electricity generation, but also on technologies to reduce CO2 emission from fossil power and industrial plants. This study next performs a technology mapping exercise for all ten ASEAN countries to determine decarbonization technologies that have high impact and high readiness for individual countries. Besides installing more sustainable renewable energies, common themes coming from these roadmaps include switching from coal to gas for power generation, using carbon capture and storage (CCS) technologies to decarbonize fossil and industrial plants, replacing internal combustion vehicles by electric vehicles, and for countries that have coal and natural gas resources, upgrading them to blue hydrogen by chemical processes and using CCS to mitigate the emitted CO2. Blue hydrogen can be used to decarbonize hard-to-decarbonize industries. Policy implications of these roadmaps include imposing a credible carbon tax, establishing a national hydrogen strategy, intergovernmental coordination to establish regional CCS corridors, funding research and development to improve carbon capture efficiency on a plant level and resolving sustainability issues of hydropower and bioenergy in ASEAN.