||Changes are reverberating through the international development system. This article focuses on (re)emerging development actors in the South and their role in setting agendas, challenging current aid orthodoxies, and rearticulating development cooperation relationships between and within the North and South. Specifically, the article examines trilateral development cooperation, a significant new trend in foreign aid. The first aim is to examine the role of trilateral development cooperation in the changing geographies of development and global partnerships. The second aim is to foreground and critically evaluate the politics of trilateral development cooperation. The authors argue that trilateral development cooperation has potential to improve aid effectiveness, harness the energies and expertise of southern partners, and reshape development relations in more egalitarian ways. Alternatively, however, it may work to co-opt (re)emerging donors into a depoliticized and ineffective aid system. While this argument has been made by many critics with regard to North–South development relations, the authors also question the projection of shared interests and essentialized developing country identities in relation to the South–South element of trilateral development cooperation. The article concludes by emphasizing the need to extend critical perspectives to all elements of the new development partnerships emerging within a rapidly changing global landscape.