The chapter aims at addressing the Education for Sustainable Development (ESD) decade from a critical perspective so that changes and their underlying tensions can be identified in the Spanish autonomous region, Catalonia. First, the political and educational background of Environmental Education (EE) and ESD in Catalonia (Spain) is addressed, and its trajectory from the seventies until the present is briefly sketched. Second, the chapter describes the four big scale EE and ESD programmes in Catalonia, Spain, during the decade, such as Environmental Education Centres, Green Schools, School Agenda 21, and the Catalan Schools towards Sustainability Network (XESC). This includes basic quantitative data as well as qualitative interpretations of the experienced changes and derived tensions. Third, the chapter identifies three quality dimensions of ESD which are important for Catalan schools today such as the ESD school curriculum, the ESD thematic choices of schools, and the participatory culture necessary to develop ESD projects. Finally, the conclusions are built around the issue of how to approach the post-UN Decade on ESD period and confront the challenges related to research on ESD, teacher education on ESD, and the internationalisation of ESD school networks.