The multidimensional and intergenerational nature of the 2030 Agenda for Sustainable Development and the Sustainable Development Goals (SDGs) calls for integrated policies. Progress made in a particular social, economic or environmental area or individual goal may generate synergies and trade-offs across dimensions (spillover effects), and steps taken in one country could have positive or negative impacts beyond national borders (transboundary effects). Assessing the multidimensional and cross-border effects of policies has become even more urgent in the context of COVID-19 containment measures. However, there are gaps in governance and analytical tools for identifying and managing spillover and transboundary effects, posing challenges for governments in designing and implementing sustainability strategies. This book, a collaborative effort by the OECD and the European Commission-Joint Research Centre (EC-JRC) presents a set of new governance and analytical tools, lessons learned from country experiences, and good emerging practices for managing spillover and transboundary effects in the implementation of the 2030 Agenda.