This article investigates the formative staffing practices of the League of Nations Secretariat. Drawing on the social theory of Pierre Bourdieu, it argues that core traits of the League's institutional capacity and identity was produced through the institutionalization of recruitment practices in the League's formative years from 1919 to 1923. Through an exploration of early negotiations and practices of staffing, we show how the League built and balanced legitimacy, by combining a clearly international make-up of the League Secretariat with acute sensitivity to state interests, and autonomy, by defending the Secretary-General's exclusive prerogative of staffing, in a way that has been defining for the trajectory of international organizations (IOs) until today. The article thus turns to the institutional landscape where the individual and its surroundings meet: through the daily staffing practices of the Secretariat, it explores how an institution came to be, function and assert its influence as an autonomous and legitimate diplomatic agent in a broader international field. As such, the article, as an innovative contribution to the field, argues that international historians should connect thorough institutional investigations with elements of the ‘cultural turn’ in International History, in order to properly engage with and understand IOs as diplomatic actors.