Sustainability is one of the new focus areas of the International Civic and Citizenship Education Study (ICCS) 2022. The European student questionnaire measured students’ attitudes related to environmental sustainability (i.e., their endorsement of environmental cooperation in Europe), and students’ behaviors related to sustainability (i.e., their reports on political consumerism behaviors and sustainable behaviors). Findings highlighted that nearly all students were in favor of different forms of cooperation among European countries to protect the environment and that this support was positively associated with higher socioeconomic backgrounds and higher levels of civic knowledge. Results also showed that students’ political consumerism behaviors and their sustainable behaviors differed widely across countries, with more than half of the students, on average, reporting having bought green products in the last 12 months or having asked their parents or guardians to do so. Across countries, most of the students reported that they have reduced the use of electricity, have reduced food waste, and have repaired rather than replaced items they owned in the last 12 months. In almost all countries, female students, students from above average socioeconomic backgrounds and students with higher levels of civic knowledge reported more frequent sustainable behaviors.