A practical guide to integrating environmental considerations into policy and sector reform for sustainable development. This resource offers a framework for Strategic Environmental Assessment (SEA) to improve policy and sector reform, focusing on developing countries. Designed for policymakers and development specialists, this guide provides tools for effective SEA implementation, emphasizing institutional capacity building and stakeholder engagement. It outlines how to achieve sustainable outcomes through environmental mainstreaming, offering a path towards economic growth, climate change mitigation, and improved environmental management. Discover how SEA can empower better policy decisions and foster lasting positive change. This volume is a collaborative effort from the World Bank, the University of Gothenburg, the Swedish University of Agricultural Sciences, and the Netherlands Commission for Environmental Assessment. It provides valuable insights and practical guidance for achieving sustainable development through strategic environmental assessment.