This article explores a paradox at the heart of climate bandwagoning. Numerous actors have hitched their efforts to climate policy formation in an effort either to advance their own interests or genuinely contribute to addressing this most urgent global dilemma or both. At the same time, the large number of stakeholders complicates climate negotiations as exceeding numbers of actors bring related but tangential issues into discussions and demand to be heard. The international community is thus faced with an almost existential situation: to address climate change in an effective manner requires nearly everyone in the room (regime bandwagoning); with everyone in the room, however, less is accomplished (regime sclerosis). This article explains such a paradox by stepping back from the cases presented in this special issue, and bringing into high relief the lineaments of regime congestion as they manifest in global climate affairs, and outlining the promises and perils involved.