This paper provides a brief overview of recent UNCTAD research on the nexus between international investment treaties and sustainable development. After sketching the historic evolution and current trends in IIA treaty practice, it explores the linkages between IIAs and three areas of public policy-making that have been at the centre of UNCTAD's research and policy analysis with respect to IIAs and sustainable development. These include 1) combating climate change, 2) integrating investment and industrial policy, and 3) promoting responsible corporate behaviour. The paper concludes on the need for more inter-State cooperation to address the various challenges facing the IIA regime today and to enhance its sustainability dimension. In this context, UNCTAD’s recently released Investment Policy Framework for Sustainable Development (IPFSD) can provide helpful guidance for the formulation of a new generation of more sustainable investment policy-making.