Education is expected to support the development of a more sustainable way of thinking, working, and living. Although there is a broad range of literature on Education for Sustainable Development (ESD), the role of principals in the implementation of sustainability and ESD in schools has rarely been taken into consideration. However, based on the results of school effectiveness research, one can assume that school principals exert a significant influence on ESD. Sustainability is a leadership issue. When a school aims at integrating sustainability and ESD, the principal plays a pivotal role. She or he has to support the endeavor wholeheartedly and credibly, organize a participative process of school development, emphasize sustainability and ESD in the daily life of the school, support teaching staff in the application of ESD, and offer students opportunities to launch their own initiatives. This article for the special issue on "Sustainability in leadership and education" is a theoretical concept paper based on a literature review and the authors' conceptual work. It offers a model and seeks to support principals in leading their schools towards sustainability. Therefore, a framework of four stages of the integration of sustainability and ESD in a school is defined. For each of these stages, a number of practical actions and management strategies are suggested and explained in detail.