The World Commission on Environment and Development in its report entitled Our Common Future has put forward the idea of sustainable development which is also an important part of the development of regional environmental law in Southeast Asia. In 1985 ASEAN Agreement on the Nature and Natural Resources has put sustainable development for the first time in ASEAN's treaty. Sustainable development continues to grow through the 1987 Jakarta Resolution on Sustainable Development agreed upon by the leaders of ASEAN. This research will look at the importance of sustainable development as part of the regional environmental international law concept and how it has grown in ASEAN today. The purpose of this research is to know the various international agreements both soft law and hard law that puts sustainable development as an important element. The results show that sustainable development has become an integral part of the regional international environmental legal system in ASEAN. A provisional conclusion shows that ASEAN's commitment to sustainable development has greatly improved the success of implementing environmental policies at the ASEAN level.