During the heydays of the transatlantic alliance between Belgium and the United States, the Belgian Ministry of Foreign Affairs built a new chancery – the office section of an embassy – in Washington, D.C. In historical research on diplomatic architecture, authors have mainly focused on the building policy of (former) great powers such as the United States, Great Britain, France and Russia. These studies examine to what extent these states have used such diplomatic building projects as an instrument of national representation on foreign soil. Similar academic research on the building policy of the Belgian Ministry of Foreign Affairs is, however, non-existent. By means of a case study on the construction of the Belgian chancery in Washington, D.C., this article sheds light on the guidelines shaping Belgium’s diplomatic building policy in the 1950s. This case study examines the extent to which the Foreign Ministry has framed this building project as an opportunity to cement the transatlantic alliance with the United States and how this was reflected in the architecture and interior design of the new chancery in the American capital. Therefore, this article approaches the Belgian diplomatic building project from a threefold perspective by touching upon the incentives of the Ministry, the architectural design and the use of the new chancery. For this purpose, this research calls upon a variety of source material such as diplomatic correspondence, archival documents of the architects, memoirs of key figures, parliamentary debates and newspaper articles.