After the entry into force of the Treaty of Lisbon, the European Parliament (EP) can give or withdraw its consent to most international agreements. This new scenario calls for theoretical models that help us to better understand the roles and strategies of European Union (EU) institutions in international negotiations. Departing from ‘two-level-games’ and principal–agent models, this article examines three interrelated elements (levels of negotiations; decision-making stages; and strategies) to explain the first international negotiations under the consent procedure (SWIFT Agreement). This case shows how the EP made use of day-to-day decision-making to informally expand its formal veto powers. The EP is now capable of controlling the EU negotiator during both the agenda-setting and the negotiation stages. Its informal involvement is set to transform its relationship with the Council and their collective capacity to influence and control the Commission.