This article explores how global citizenship can be seen in the practices of science education in the context of international education policy and Finnish school and teacher education, with a focus on scientific literacy and sustainability education for promoting a sustainable future. Possibilities of science education to promote sustainability are discussed through teaching examples based on socio-scientific approaches. In addition, transformative science education for sustainability is regarded through competence development taking into account different knowledge dimensions. Solving problems however requires not only knowledge but also communicative and strategic and speculative activity. Thus, education must emphasize the main visions of scientific literacy and transdisciplinary perspectives proposed in the literature, supporting students to understand society and everyday socio-scientific challenges from the local to global level and to deal with differing scientific results and uncertain information. Our article presents findings and conclusions that provide opportunities for further work and provide insights into science and educational sustainability practice.