Bringing together managers from different countries and cultures after international mergers is often seen as beneficial for the development of multinational companies. The article refers to existing approaches in the literature on modern cultural management and the organisation of multinationals to develop a framework explaining when and in which way national diversity affected the composition of the governing bodies and the strategy of the company. It therefore focuses on the nationality of owners and managers and asks to what extent corporate nationalities persisted after the merger and if single national groups determined the strategy. Based on original archival material the case of the Dutch-German man-made fibre manufacturer AKU/VGF/Akzo illustrates that its ownership structure depended to a large extent on political circumstances and that changing corporate nationalities shaped the governance of this company. Our study contributes to opening-up the black box of the composition and organisational structure of multinational boards and the locus of decision making within multinationals.