The influence of the European Union on national power structures, actors' institutional opportunities, and governance networks is well established in cases of Europeanization processes unfolding in member states or associated countries for which a formal agreement is in place. This article focuses instead on Europeanization processes that are more informal and do not include formal agreements but bottom-up dynamics. Empirically, we analyze the collaboration network in Swiss energy policy with Exponential Random Graph Models and find that actors with EU contacts and those that consider the international process as important are particularly active in the domestic governance network, whereas actors considering the domestic process as strongly Europeanized and those with pro-EU beliefs are particularly inactive. This points towards a complex influence of informal Europeanization on domestic governance networks.