This paper examines the role of the rotating Presidency in the external representation of the EU in international environmental negotiations after the entry into force of the Lisbon Treaty. Focussing on two negotiation sessions under the 2010 Belgian Presidency, the biodiversity negotiations in Nagoya (October 2010) and the climate change negotiations in Cancún (December 2010), the paper’s aim is fourfold. First, it explains why the entry into force of the Lisbon Treaty has not changed the existing practices with an important role for the rotating Presidency. Second, the paper discusses the developments in the debates on the EU’s external representation on environmental matters. Third, it empirically analyses the way the EU was represented in the biodiversity and climate change conferences of 2010. Here, the paper also points at the increasing importance of the so-called ‘practical arrangements’ that settle the external representation of the EU on the floor, often in a very ad hoc manner. Fourth, the paper describes how the European negotiators in Nagoya and Cancún have dealt with their representation task that generates a tension between expectations coming from the international level and pressures originating at the EU level.