Increasing attention has been paid to sustainable development in investment treaties and forums recently. European Union (EU) advocates for sustainable development and offers respective provisions in their investment treaties. Recent developments of the Association of Southeast Asian Nations (ASEAN) members’ agreements also shed light on the investment and sustainability nexus. The chapter argues that the EU’s model of sustainable development accords with ASEAN’s intrinsic demand for increasingly addressing investment and sustainability. This is a priority for not only developed countries but also developing countries during their investment treaty negotiations. It also envisages that sustainable development provisions in an investment chapter in the prospective ASEAN–EU Free Trade Agreement (FTA) can inherit from investment agreements, to which some ASEAN members and EU are contracting parties.