This article analyses public–private partnerships in Belgium’s economic diplomacy from the perspective of multinational companies (MNCs). The concept of corporate political activity (CPA) is therefore introduced. CPA is seen as a part of business diplomacy (BD), which companies use in order to defend their interests. Eight stock-listed Belgian multinationals (BMNCs) were interviewed using single, semi-structured interviews. This exploratory study focused on whether or not companies contact public officials, which strategies they use and how these strategies are organized in order to defend their interests abroad. The empirical data revealed that BMNCs enter into relationships with national and supranational actors. Information-sharing is the central aim of these relationships, because of the mutual realization that these contacts are important. This was less so, however, at the international level. In short, BMNCs will, depending on the subject and/or the institutional context, rely on the services offered by Belgian economic diplomacy. They will initially, however, also include diplomatic functions of their own.