The Westphalian idea of sovereignty in international relations has undergone recent transformation. "Shared sovereignty" through multilevel governance describes the responsibility of the European Union (EU) and its Member States in tobacco control policy. We examine how this has occurred on the EU level through directives and recommendations, accession rules for new members, tobacco control campaigns, and financial support for antitobacco nongovernmental organizations. In particular, the negotiation and ratification of the Framework Convention on Tobacco Control (FCTC) and the participation in the FCTC Conference of the Parties illustrates shared sovereignty. The EU Commission was the lead negotiator for Member States on issues over which it had jurisdiction, while individual Member States, through the EU presidency, could negotiate on issues on which authority was divided or remained with them. Shared sovereignty through multilevel governance has become the norm in the tobacco control policy area for EU members, including having one international organization negotiate within the context of another.