Network concepts are central to at least three challenges of interest in the sustainability science literature: how to link knowledge with action, how to enhance collective action, and how to promote social learning. Although each challenge has developed into a coherent literature, social network concepts—which examine the particular ways in which social agents relate to one another—emerge as a common theme across all three challenges. To build a synthetic understanding of networks and sustainability, we must consider how structural properties of networks relate to sustainability outcomes, how networks evolve over time, and how institutional context influences this evolutionary process. A better understanding of these questions can inform strategies to promote patterns of social interaction that support sustainability.