The role of teachers in Education for Sustainable Development (ESD) is defined by examining how pre-service and in-service teachers become change agents by acquiring education for sustainable development competency. Through formal and informal professional development given by academic institutions and non-profit organizations, teachers can acquire a knowledge of sustainability. In the context of teaching for sustainable development, tertiary institutions and non-profit organizations play a significant role in developing capacity and preparing preservice and in-service educators. Specifically, the duty of K-12 teachers is to promote the shift toward sustainability in their teaching techniques. Teachers with a solid knowledge foundation on sustainability will be better prepared to manage the ever-changing nature of the world and will be able to teach their pupils the required information, skills, and attitudes in sustainability, culminating in sustainability literacy and action. Nonetheless, integrating ESD into pre-service teacher education remains both a chance and a challenge. This Guidebook recognizes that if teachers are to effectively contribute to attaining sustainable development, then ESD must be incorporated into pre-service teacher education.