Development economics was born as a distinct disciplinary field in the aftermath of World War II, when the development of so-called Third World countries, due to the dynamics of decolonization and the Cold War, became an international priority. At the institutional level, the birth of development economics was paralleled by the reorientation of the International Bank for Reconstruction and Development (so-called the World Bank) from the support of European reconstruction to funding development policies worldwide. Not surprisingly, the paths of the Bank and of pioneers of development economics often crossed, and it is fair to say that the Bank and the new discipline—from the perspective of the history and sociology of social sciences—are part of the same story. Indeed, one would think that the Bank was the natural place for the breeding of development economics. This seems coherent with the image we have of the Bank today: the reign of economists. Yet, for most of the years when development theory was shaped, the Bank, although very active in development policies worldwide, was remarkably silent in the field of development economics. This paper will connect the study of economic ideas and economists in international organizations with the history of economic policies. Based on previously untapped archival sources, it will discuss how the history of development economics and of development organizations—and especially the largest among them, that is, the World Bank—proceeded separated for a long stretch of time, and how they later converged.