In recent decades, local government has become increasingly affected by EU-regulations. Yet simultaneously, the EU offers a new opportunity to promote local interests, for instance by lobbying its decision-making process. This research project will investigate the effectiveness of the municipal lobby in Europe. More specifically, it will determine which conditions explain influence of local government on European decision-making through lobbying. In the academic literature, such process is labeled ‘bottom-up Europeanization’ or ‘regulatory mobilization’. It represents a specific case of EU interest group politics and includes action from single towns and cities, as well as different national and European networks and institutions. On the basis of the current state of the art, we have constructed a theoretical, causal model of the municipal lobby in the EU that we will test in our study. The model comprises different contextual elements and characteristics of the municipal interest group. Together they constitute particular paths to lobby influence. The contextual elements are the existing legal framework, the conflict on and nature of the policy issue. The interest group characteristics include structural position, information, type of interest and strategy. We will test our theoretical model with QCA, comparing 12 divergent cases of the municipal lobby in the EU. Data are collected through document analysis and semi-structured interviews with policy actors.