This article examines the relations between the European Parliament (EP) and civil society organizations (CSOs) in the EU’s legislative process. It focuses specifically on legislative trilogues, an informal institution bringing together the representatives of the EP, Council, and Commission in a secluded setting to conclude legislative agreements. Trilogues have become the modus operandi and an absolutely pivotal part of the EU law-making process: they are where the deals are made. While secluded decision-making offers plenty of opportunities for EU institutions to depoliticize law-making, we argue that trilogues have become politicized, partly from the relationship between the EP and CSOs. We flesh out this argument on the basis of insights from the politicization and the historical institutionalist literatures, advance two ideal types of trilogue politics, and explore these types on the basis of a preliminary examination of a comprehensive interview material.