International relations research has in recent years become more relevant for international lawyers, even if it often requires some translation. This chapter engages with three bodies of international relations scholarship of relevance to understanding UN treaty-making. The first, on norm dynamics, has a unit of analysis smaller than a multilateral treaty; a norm typically equates to one or more of the substantive provisions of a treaty. The second and older body of literature, on regimes and more recently regime complexes, has generated insights pertaining to treaty design and effectiveness, often through the application of quantitative research methods. Given that there has been two-and-a half-decades of regime research the contribution of regime theory to knowledge of multilateral treaties nevertheless remains underwhelming. The third body of literature addressed in the chapter is that regarding the decline of the liberal international order. Liberal institutionalist scholars may be lamenting the apparent demise of the US-led order to which the complex web of UN treaties has been so integral but they may not be sufficiently conscious of the fact that such a sentiment is not universally shared. Understanding the politics of multilateral treaties can only be enriched by an even greater maturity and sophistication of international relations scholarship.