The purpose of this study is to examine the role of the International Bank for Reconstruction and Development (World Bank) in the formation and implementation of Iran’s First Development Programe during the years 1949 to 1955. Adopting a historical–institutional approach and based on official documents and reports, the research analyzes the Bank’s involvement in planning, consultation, financing, and project evaluation related to the First Development Plan. The findings indicate that the loan expected from the World Bank, which was one of the two main intended sources of financing alongside oil revenues, was not realized due to the political upheavals following the nationalization of the oil industry and the subsequent crises. Nevertheless, the World Bank played a significant role in shaping the content of the plan and determining development priorities through advisory frameworks, the dispatch of expert missions, and the assessment of proposed projects. This collaboration not only influenced the institutional structure of the Plan Organization but also established Iran’s first direct experience of engagement with an international financial institution an experience which, although it fell short of fully achieving the plan’s objectives, strengthened the intellectual and institutional foundations of development planning in the country.