This bachelor thesis aims to assess the historical and present influence of economic interest groups on the bilateral negotiations between Switzerland and the European Union. As Economiesuisse has been a prominent economic interest group since the start of Swiss-EU cooperation, it will be the main subject of this thesis. Theoretical perspectives involving commercial liberalism, liberalism in foreign policy, and, most relevant, Putnam’s two-level game theory, will structure the analysis. Methodologically, this thesis consists of a case study based on administrative documents, letters, news articles, and archival records. Additionally, two interviews were conducted, one with an academic scholar and one with a Swiss official.The key findings of this thesis show that while an immediate influence is not visible initially, Economiesuisse’s position on bilateral negotiations has been requested by the Swiss Federal Council in all crucial phases amongst another selected small group of associations. Furthermore, Economiesuisse’s influence is noticeable, as seen from its history, member count, and active presence in Switzerland. Considering their lobbying efforts in the past and today, a considerable influence is therefore clearly attestable to Economiesuisse.