The focus of this chapter is the puzzle about why it has taken so long for the G20 to be taken seriously in institutionalist international relations, and whether this evolutionary pattern matters for addressing the pivotal question: “How International Organizations Promote or Detract from Peaceful Change.” Amid the shocks of the Global Financial Crisis, the G20 became the privileged institutional choice over alternative options via formal International Organizations, including the United Nations. The protracted lack of scrutiny on the G20 in institutionalist IR is puzzling given the role of this scholarship in extending the level of analysis not only with an original focus on formal IOs but also an expanded range of informal institutions. Per se, the extended neglect of the G20 is a symptom of an ingrained Western and more specially the US centrism in the literature. Even as the G20 has lost instrumental purpose, the value of the G20 as a vehicle for management of world politics must be recognized. The lack of understanding concerning the evolution of the G20 in mainstream IR is particularly noticeable with respect to the elevated role in the G20 by countries with Global South identities.