Hydropower has a long track record of providing affordable and reliable electricity to various regions of the world throughout the decades. However, diversity in the type of hydropower plant installations results in an array of social, environmental and economic impacts linked to financial and technical challenges that must be accounted for and should be managed. To that end, sustainable practices in hydropower are reinforced at the international level, and sometimes embedded into legislation, through programmes, trainings and the use of frameworks and tools. The International Hydropower Association (London, UK) has developed with various stakeholders of the hydropower sector, the Hydropower Sustainability Environmental, Social and Governance (ESG) Gap Analysis tool (HESG), an assessment tool that aims to define and assess sustainability performance of hydropower projects and facilities. This work shows how the application of the tool, which is infused with sustainability principles developed in the ground-breaking Brundtland and World Commission on Dams reports, contributes to fostering sustainability in the hydropower sector through the example of the Dibwangui hydropower project assessment in Gabon; demonstrates the alignment of the HESG with the International Finance Corporation (IFC) widely used Performance Standards; and explores new development avenues and uses of the HESG, as observed with the Hydropower Sustainability Standard.