External actors’ science diplomacy is essential to catalyze low-carbon transition in Southeast Asia, as countries in the region face structural hurdles to achieve their nationally determined contributions. This chapter seeks to answer the research question: to what extent is China shaping low-carbon transition through the use of science diplomacy towards Southeast Asia? Throughout our research, we have drawn three observations. Firstly, Beijing demonstrates clear willingness to use science diplomacy to foster low-carbon transition in the region, evidenced by the codification of its willingness into various policy documents and government statements. Secondly, China has certain capacity to promote low-carbon transition in Southeast Asia, in view of the established institutions, available financial resources, and instrumental mechanisms. Meanwhile, the acceptance of China’s science diplomacy from the recipient states differ. In some countries, China’s activities in the field of infrastructure have eclipsed its image as a responsible stakeholder to promote climate actions. Overall, perceptions from the general public seem to be negative, while local elites’ opinions about China are mixed. Consequently, the lack of acceptance of China’s role in fostering low-carbon transition in the region may concede a greater role for other actors to step up their science diplomacy towards the region.