Cooperation helps states realize mutual gains, but mistrust and disagreements over institutional design inhibit cooperation. This article develops a network explanation for how states achieve cooperation in the face of persistent coordination and collaboration problems. The analysis focuses on bilateral cooperation agreements, a vast body of treaties spanning multiple issue areas. Bilateral agreements constitute an evolving network of cooperative ties. This network defines the strategic environment in which states bargain over new agreements, endogenously influencing subsequent bilateral endeavors by revealing strategically valuable information about states’ trustworthiness and preferences over institutional design, while also generating externalities that incentivize bilateral partnerships. Inferential network analysis shows that states are more likely to create bilateral agreements if they (1) share agreements with common third parties, (2) accede to more agreements in general, and/or (3) share important exogenous characteristics with current bilateral partners. These network dynamics drive bilateral cooperation in everything from commodities to cultural exchange to fisheries.