As the world experiences heightened levels of violent conflict and polarization, understanding what peacebuilding efforts are “effective” becomes all the more pressing. This groundbreaking edited volume brings together a diverse, global group of practitioners, researchers, and peacebuilders to grapple with urgent questions and challenges related to defining and assessing peacebuilding effectiveness. Sections of the book engage in critical reflection on what peacebuilding effectiveness is and who gets to decide, provide practical examples and case studies of the successes and failures of assessing peacebuilding work, and support innovative strategies and tools to move the field forward. Chapters reflect a variety of perspectives on peacebuilding effectiveness and methods—quantitative, qualitative, and participatory—to evaluate peacebuilding efforts, with particular attention to approaches that center those local to the peacebuilding process. Practitioners and policymakers alike will find useful arguments and approaches for evaluating peacebuilding activities and making the case for funding such efforts. This book aims to catalyze conversation and action among peacebuilding practitioners, academics, donors, and those directly affected by peacebuilding efforts about how we define and measure effectiveness.