Collaboration among international institutions is essential for high-quality governance in many areas of global policy, yet it is chronically undersupplied. Numerous opportunities for institutional collaboration are being missed and there are calls for deepening collaboration in discourse on global governance — in new areas of governance, such as digital privacy, content moderation and platforms; better-established areas, such as climate change and biodiversity; as well as long-established but nonetheless evolving areas, such as international finance, development and trade. There are several obstacles to collaboration, including key countries’ using some institutions to constrain others, a strategy of “complexity for control.” This policy brief suggests that in designing international institutions, states and other principals should draw from a tool kit of strategies and techniques for promoting collaboration, including introducing or developing formal and informal mechanisms, and harnessing the Group of Seven and the Group of Twenty to foster collaboration proactively. New institutions should be designed from the outset to collaborate with others in a dense institutional environment.