Sustainability or ‘sustainable development’ is a multi-faceted concept that has been inserted into different sources of international investment law. This multi-layered nature explains the wide variety of aspirations introduced in the ‘2030 Agenda for Sustainable Development’ and its 17 different Sustainable Development Goals (SDGs). However, there is still no clarity on what is the appropriate standard that international investment law adjudicators should use reviewing the ‘multi-faceted disputes’, where the parties refer to two or more of the facets of sustainability—economic, human rights, environmental or good governance—in their arguments, either as a central argument or as additional or secondary reasoning. The project aims to provide such a standard of review by analyzing how the concept of sustainability has been put forward in the international investment law jurisprudence. Then, the project will find inspiration within the broader international legal domain looking at how other adjudicators had solved multi-faceted sustainability disputes. In particular, standards of review of sustainability will be explored in the three regional human rights courts. The results of the project will allow a more consistent practice on the use of the concept of sustainability in international investment law litigation.