At the 26th Conference of Parties (COP26), the world economies have re-pledged to collectively attain the global objective of ensuring environmental sustainability, especially by adopting credible initiatives that can address the environmental problems experienced worldwide. Accordingly, this study aims to assess how environment- and energy-related technological innovations contribute to the establishment of this objective across South and Southeast Asia, Notably, this study proposes a new composite environmental sustainability index using environmental data from different dimensions. Further, considering data from 1996 to 2019, the results derived from the econometric analyses confirm that environmental innovation is effective in facilitating environmental sustainability only in the context of Southeast Asian countries while energy innovation is effective in doing the same for both South and Southeast Asian countries. Besides, for both cases, good governance is evidenced to directly promote environmental sustainability and also indirectly facilitate it by jointly reducing the environmental problems along with environmental and energy-related technological innovations. Moreover, greater urbanization and more involvement in economic globalization-related activities are observed to inhibit the prospects of establishing environmental sustainability in the concerned South and Southeast Asian nations. Furthermore, the results certify that compared with the South Asia the prospects of achieving environmental sustainability are relatively higher across Southeast Asia. Based on these critically important findings, a couple of policy-level suggestions are provided.