This study examines discourse about sustainability education (SE) in Icelandic preschool curricula and their alignment with the Icelandic National Curriculum Guide for Preschools of 2011. Historical discourse analysis was used to analyze the curricula set by 16 preschools, focusing on how SE in early childhood education is viewed by the educators who write preschool curricula. The study draws on theories which argue that children’s participation is crucial in democratic societies. Major findings show that while preschool curricula include SE, their interpretation of sustainability were typically not broad enough to match the recommendations of the National Curriculum Guide. Rather, they focused on environmental and economic issues with scarce attention to the sociocultural aspects of sustainability and children’s participation. In response, the discussion and conclusion suggest how issues of equality and welfare, along with children’s democratic competence and children as agents of change for sustainability can be developed in this context.