This chapter examines research on nonstate governance institutions in the shape of diverse sustainability certification programs. I review research findings and insights related to two main analytic themes: the emergence and evolution of sustainability certification programs, and the effectiveness of these programs in resolving or ameliorating the problems that motivated their establishment. While we know a great deal about the emergence and evolution of sustainability certification, more research is needed to better understand its achievements and challenges, as well as the institutional and longer-term consequences of certification programs. There is a need for cumulative research beyond single-case studies in order to understand patterns of institutional evolution and change, the direct effects and broader consequences of certification, program interactions, and certification’s intersection with governmental, intergovernmental, and civil society initiatives to address environmental and social problems arising from the practices of global production, distribution, and consumption.