This chapter introduces and discusses the concept of willingness to act pro-environmentally, as an important component of a wider set of non-cognitive outcomes of education for sustainable development. The relationship between citizenship, sustainable development, and willingness to act pro-environmentally is explored, elucidating how the latter might account for newer forms of citizenship and the role of educational systems in this process. Building upon these considerations and utilizing data from the International Civic and Citizenship Education Study (ICCS) 2016, the differences between countries in the willingness of eighth graders to act pro-environmentally in the future is analyzed and compared with various other participatory intentions. The chapter provides insights into the percentage of students willing to make efforts to sustain the environment when they become adults across all participating educational systems in ICCS 2016 and explores the relationship of this distribution with key country attributes, such as national richness and pollution indices.