Chapter 13 analyzes his contributions to development economics. It is argued that his central contribution is not an economic theory of development, but rather a technique for development planning. Tinbergen’s work on planning is mainly concerned with implementing development plans, which he argued should be done using his three-stage planning model, consisting of the macro phase, the industry phase, and the project phase. Later work expanded this model to include regional planning and education planning. After the initial period between 1955 and 1960, most of Tinbergen’s work on development economics was increasingly about a vision of an integrated world economy. It is demonstrated that econometric and analytical work moved to the background and that his visionary and institutional work moved to the foreground. Crucial in his vision of the international economic order was his experience in the Netherlands. The chapter shows how his vision of the international economic structure crucially relied on analogies with the national economic order. The chapter concludes with some early reflections on his development economic work and suggests that it largely disregarded the ethos of self-help and emancipation that Tinbergen knew from his youth in the AJC.