Within the context of sustainable development, social workers have important roles to play towards the eco-social transformation of society. This chapter starts by justifying how social work and sustainable development are linked. Then, it defines eco-social work and considers implications for education, research and practice of social work. The chapter provides examples of how the social work unit at the University of Gävle contributes to sustainable development through its education, research and community engagement. The chapter concludes that sustainable development is an area  of legitimate focus for social workers, and sustainability is a core social mission of social work.