Sustainable energy systems are one of the major and pressing challenges of society, science and industry. In this regard, the Helmholtz research program Energy System Design (ESD) aims to support the transformation of energy systems through the development of methods to design, validate and assess societally feasible transformation pathways. This Website aims to present on-going work within the Helmholtz Working Group on MCDA for sustainability assessment as part of the Helmholtz program ESD. Our work is structured alongside four fundamental components of MCDA-assisted sustainability assessment, namely problem definition, sustainability criteria, MCDA methods and stakeholder’s integration (see Figure 1).