ABSTRACT This research article takes one step to investigate bargaining in international politics and shows how institutional dynamics influence a regional institution’s ability to realize the own set policy goals. The chosen case, the trade negotiations between the EU and MERCOSUR, presents a way to assess both institutions abilities and dynamical underpinnings in the interaction with each other. Based on a qualitative research design, the article examines the experiences of negotiators on both continents that have directly participated in the EU-MERCOSUR negotiations. The results show that while a high degree improves learning processes, expertise, and external legitimacy, it bears a high risk of rigidity and therefore, failure. The research article draws precise conclusions for the way we study regional institutions examining how their set-up influences strategic choices.