In May 2013 the Conservative government decided to renegotiate the terms of UK membership in the European Union and to call for an in-out referendum. In June 2016, 51.9 percent of the voters spoke out in favor of leaving the European Union - an outcome which has ultimately triggered a novel process in European integration: differentiated disintegration. In a political system of regional integration, this term refers to the selective reduction of a member state’s level and scope of integration. This chapter theorizes the negotiating structure of differentiated disintegration and examines the ongoing negotiations between the EU and the UK. It argues that the institutional and material bargaining power of states demanding disintegration is considerably lower than that of states demanding opt-outs in the context of integration negotiations. This negotiating structure has ultimately caused the UK government to make concessions on the withdrawal agreement and moderate its demands on the future relationship with the EU.