This article explores the extent to which the growing party politicization of the EU extends to the European Council. We advance the argument that three central factors shape the extent to which party politics influences European Council outcomes: the salience of an issue along the left-right dimension, the partisan composition of the European Council, and the cohesion and mobilization of transnational parties. We explore the influence of these factors empirically through an inventory of elite interview evidence as well as two case studies - the employment chapter of the Amsterdam Treaty and the Lisbon agenda. We conclude that the conditions for party influence in the European Council are demanding, and that the scope for party politicization is less extensive than in the other major EU institutions. The issues on the agenda of the European Council often cut across partisan divides, the heads of government are seldom mobilized along transnational party lines, and decision outcomes instead tend to reflect issue-specific coalition patterns