In the curricula of many countries, sustainability education is the responsibility of teachers of all subjects, including science teachers. This chapter will show that teaching science from a sustainability perspective may prove challenging for science teachers because such a perspective draws on knowledge structures and teaching traditions that lie outside of the realm of science. Based on an analysis of the didactical questions of “the why,” “the what,” and “the how” these challenges will be outlined, which include the normative perspective on education, that is, including values and emotions in addition to scientific concepts, and the inclusion of an anthropocentric perspective. Also, the complexity of sustainability issues calls for multi- or interdisciplinary perspectives, while the “wicked” nature of sustainable development (as opposed to the “tame” issues science commonly deals with) makes it difficult to apply predefined solutions, which is a common approach in science education. A possible way to overcome these challenges is applying a cross-curricular approach to the organization of sustainability education in which teachers representing separate subjects or disciplines collaborate. It can be argued that this complementary perspective could widely benefit science teachers, who could focus on contributing to sustainability education based on their specific disciplinary competencies rather than reorienting their teaching in a way to accommodate the challenges associated with providing a comprehensive view of sustainability.